Background processes are 100% limited in iPadOS in relation to macOS: it’s hardcoded in the OS. The way iPadOS and iOS manage background processes inherently limits them. It is not just in a Developer’s control. iPadOS and iOS more aggressively shuts down background processes compared to macOS and virtual memory wasn’t even really in existence in iPadOS until more recently. But virtual memory in iPadOS is still limited compared to macOS and doesn’t do much relatively outside of managing Stage Manager.
It’s an achievement to run two processes at once in iPadOS, like rendering something in one App and then exporting a movie in another App. Although that is still elusive. Examples of music playing in the background isn’t really notable multi-tasking… that has been around basically since day 1.
In macOS, you can have effectively UNLIMITED background processes. You can be exporting a project from FCP, exporting a project from iMovie, rendering something in AutoCAD, exporting a project from Logic Pro, saving a Word document to a folder, streaming YouTube, formatting a hard drive, all with 400 tabs going in Safari.
There's a small list of services apps are allowed to do in the background, unlike macOS. iOS and iPadOS use more memory swapping as opposed to virtual memory in macOS. iOS and iPadOS save states of apps so the app on your screen has most of the system memory and is the result of iOS and iPadOS being designed with flash memory.
Even with all of the operating system limitations, I’ve seen M class iPad Pros get less than 3 hours of battery life running professional apps and even have heat warnings on exporting files from FCP. Imagine if macOS was unleashed on the iPad: battery life would be measured in minutes for some and it would throttle the CPU to a screeching halt because of heat.