[1] https://developer.apple.com/documentation/security/disabling...
[1] https://nektony.com/how-to/uninstall-default-apple-apps-on-m...
Second, and perhaps more awkward, is you're actually still wrong. I didn't assume that what you claimed couldn't be done because I didn't know how to do it, but because of, for example, the fact that I was actually at Apple when this change was rolled out, or that I've gone through the processes in the article you linked enough times to know how they work.
Anyways, turning off SIP does let you just go rm everything you want. That used to be the case, until Catalina, but it isn't anymore. In macOS Catalina those files were on a separate mount that was read-only, but with SIP disabled you could remount it as read/write and then work with it as usual. In Big Sur the entire volume has been turned into a signed APFS snapshot that you cannot modify, period. Even if you pull off hacks to patch it the system will panic on the next boot (as several iOS jailbreaks have found out the hard way). What you can do on macOS is shut down the computer, boot into recovery, disable signature verification, and from there create an entirely new snapshot with the modifications you like. With just SIP disabled and root permissions you can't do this, and even if you go through the process I described it's irrelevant whether macOS is a BSD or apps are in bundles because you're literally constructing a new copy of a APFS volume with the contents you want.
This is not possible on iPhone though. You can't even run any other browser than (reskinned) Safari.
mobile Safari is embedded in iOS. It can be deleted by jailbreaking and gaining root access, but removing it would cause iOS to malfunction. You can't delete it entirely from iPhone, but you can effectively delete it by removing it from the Springboard, entirely disable it in Settings (using Content & Privacy Restrictions, toggle the switch next to it in Allowed apps), and make it undiscoverable.
And although all web browsers on iOS use WebKit, there are effectively only two browser rendering engines still used today, WebKit and Gecko. And only FireFox uses Gecko. Every other browser uses WebKit or an engine derived from WebKit. So while Apple considers allowing the other rendering engine,[1] Gecko, I guess you're stuck using any other browser other than the official Gecko version of FireFox. There's a WebKit version of FireFox for iOS, if you can stand to use it.
[1] https://9to5mac.com/2022/12/13/apple-mulls-opening-browser-e...
Thankfully, the EU is forcing Apple's hands, and soon we'll see better browser engines running on iOS.
Microsoft was blocking competitors by requiring a fee for every processor sold by a manufacturer that offered Windows, whether that machine was sold with Windows or not, causing any other operating system sold on licensee machines to be more expensive for consumers. It wasn't bundling that was the issue in Microsoft Corp v Commission, it was tying applications together, such that if you purchase one application, you are forced to purchase another.
I don't see how it relates. Apple bundles software but does not sell what it bundles, nor is the consumer unable to remove that software, unlike with Microsoft Windows and Explorer. You can delete Safari and every application Apple bundles, and you can not purchase it because it's free with the hardware.