As iOS user I couldn’t care less if it was.

Extension points have existed for much longer than Android has. The Mac has had them since at least system 6 (1988). Photoshop has had them since version 2.0 (1991)

This is not correct. That's not an Extension Point. That's a plugin interface. Extension Points are a type of plug-in, but have the specific feature of not running in the host application's address space meaning that many types of bugs and security attacks are not possible. For example, if an Extension Point dereferences NULL, it will crash, but the host app can restart it and reconnect without losing any data. If a Photoshop plug-in dereferences NULL, Photoshop crashes.

Ah, yeah, that's an interesting distinction I hadn't thought of. Any idea what the first example of that type of extension was? My gut says that'd still been done long before android

IPC has been a systems feature for a while, but discovery is a higher level thing needed for this sort of plugin interface. COM and CORBA are ancestors I know about.

not any more than a filesystem is an "Android feature" because Android also has a filesystem API.

Such APIs have been around since the 90s, if not earlier. MS OLE, OpenDoc, Classic Mac's "Publish and Subscribe" API, I'm pretty sure OpenStep had something similar (which would be Apple's IP today, and predates Android by half a millenium).