You are correct, it doesn't matter.
There's the reality and then there's marketing.
For the record, I've had both consumer iMacs and Pro Macs including updated Mac Pro's and two iMac Pro's, The iPad is a different thing altogether and it's not in the same species, it's tied to the post processing and image smoothing functions that make the scroll functions seem less strained. It's like oversampling in audio. the higher the rate, the more antialiasing and more post process is necessary to bring it back to human hearing range but it only works when the components are matched and the software is balanced to define and control it properly. The true motion display is an interesting idea but if you dive into the technical brief on it. It's a very close relative to AMD's free sync and I wouldn't be shocked to see it appear in an iMac design somewhere soon. It already exists in the XDR display. you aren't seeing 120 frames or even 60, you're seeing a balancing of post processing and intelligent adjusted workload output. the real magic to those is that it does present a better picture at a lower power consumption because of variable frame rate and post processing, not because of high frame rate in itself.
that's where my comment about the display overdriving comes in.
As far as mismatching > get a breakout component list of your Mac models sometime and go line by line down the list with the component level list of your hackintosh parts. You're going to find they don't match up component for component and that's where the mismatch statement comes from. It takes very very little to throw a curve when what the system expects is there and more when something it didn't expect is there. If it really was a mix and match thing, they wouldn't make closed systems and they wouldn't protect their sourcing or refurbishment supply lines the way they do. it's all proprietary from the ground up. Custom boards, UEFI roms, Custom support chips.> some overlap with available parts - sure but not really the same and even the bootloader veterans will say proceed with patience and caution and don't expect immediate gratification or success and absolutely do not expect 100% compatibility or a 200% improvement in performance with any given application or function.
Just a guess but they might know what they're talking about on that point and I agree with them.
Do some reading on the MacOS kernel and how it interacts with both the efi and the system hardware, it's threading capacity and why it's balanced the way it is. Better still take a look at the hackintosh forums where there's been several long running threads about trying to build system with more than 32 or 48 cores and the lengths they had to go to to make them function meaning boot..sort of (it's really cool stuff in that gene wilder, "Igor...you say you brought me an abnormal brain?" kind of way). most of the extracts and white papers are available in the dev section of apple - I never bothered with a hackintosh because it never offered any advantage over a Mac Pro system in either expandability or in it's ability to use resources and still doesn't. The gap is just getting wider with the new one. The seawall is going to set the standard for the next five years in what the desktops will have to catch up to. It's going to be interesting times to see if the motherboard and component makers take up the challenge on the pc side. I don't think they will.
Back to your original question: The reason it seems like IOS gets the performance lifts is because they are still refining development for that series of processors they update and enhance the silicon every cycle and the last few revs have been dramatic shifts. Intel has not made a change in their fundamental core architecture in nearly 15 years since the original cores were introduced, yes they add things > small things and baby step functionality, but the core silicon remains the same as it's been since they moved away from the Pentium II and itanium projects. What can be refined and exploited now is threading and scheduling and they've done powerful work in that with their core pro apps, but it's not a new architecture and it's going to be that way for a little longer Until Intel unveils their challenge/mate to the ARM series in a true 64 bit architectures without the legacy silicon baked into the die and a path to 128bit. Which according to Intels roadmap is less than 2 years out - if they can get their chip fabs up to speed on a process that makes it feasible. I think that's when you'll see the kind of performance marketing return to the WDC presentations for MacOS at the OS level and the app development level.
To close this, I wasn't making fun of you and I am sorry you took it as that. I do think the hype and the misunderstandings of how these things actually work is a little crazy and we do live in a world where the information is available and it's in anyones best interest to dig in and get familiar with it if they really want to get the best out of it and understand why it gives a given benefit or limitation. It makes better consumers, a better experience in value for money and a much smaller footprint burden on supporting those technologies and their bells and whistles and what is realistically expected.