I wouldn't use the word "compromise" here. But I don't have a word for it at the moment either. Perhaps the closest would be "blasphemous". What I am giving up is not something tangible like performance or battery life that can be quantified on a spreadsheet. Rather, it's like the very "essence" of the device that's at stake here.
An iPad with 2 separate OSes on it may sound like the best of both worlds in that users could in theory just boot up whichever option they wanted at any one time, and you are probably right in that I wouldn't lose anything apart from some space to housing an OS I may never really use. However, I feel it goes against the grain of what drew me to Apple products in the first place - their minimalism, their "zen", and above all, the trust that Apple does know best.
This is why I like product designs that are opinionated. The best example to me is the 12" MacBook with 1 usb c. Yes, it was slow, had only 1 port, and you can probably list off a ton of other comprises, and that to me was the whole beauty of it. That Apple had the conviction to say "we believe that this one feature (ultra-portability) is worth more than every other tradeoff combined". It may not have been very popular, but the important thing was that Apple believed, and they believed it enough to put all their engineering and marketing behind it.
And that, I respect. Even if the end product isn't to my liking, and even if compromises have to be made to fit said product into my workflow (like tons of dongles). Maybe it's sunk cost fallacy speaking, but I did invest a lot of time and effort into making my iPad, and work well it did for the stuff that I did use it for, and I am thankful that the iPad was sufficiently differentiated from my Mac because the work I was doing on it couldn't be readily replicated on a conventional PC form factor to begin with. That's why I sought out something different in the first place.
That's also why I feel it's a shame the current line of MBPs did not stick with their all USB-C port selection. I can admit that having a HDMI port can make it infinitely more useful in some situations, and users did get MagSafe back, but at the same time, there was this elegance and purity in a device having nothing but usb-c ports. Heck, the sides even looked better. But hey, the new line of MBPs do seem to be better received, and I guess the market ultimately speaks out louder than I ever can.
I have gone through more than a decade of people screaming at me online about how Apple products are overpriced and how Apple deliberate gimps them and how I can get more for less elsewhere, and I continue to remain an Apple user throughout. To me, Apple products have never been about having the most features, or being the "most useful", but about distilling the purest mixture of form and function possible. That to me is what I look for in an Apple product, not a huge feature list. Having multiple OSes on an Apple device just feels antithetical to the design-led philosophy that Apple espouses.
I don't know if I am making sense here.