@Curt: Thanks, yes. I think I understand what you say there, but the control over the ongoing availability of the defined extensions is arguably the crux of the matter.
I mean, for example, what if the extension you want (as listed by Share Extension or Extension List Dumper) is no longer available in the store? - like BadAdJohnny, for example.
I would surmise in that case that BAJ was probably excommunicated ostensibly (at least) for its links with a VPN, but that doesn't alter the fact that it was/is a pretty devastatingly good adblocker, and it doesn't consume gigabytes of RAM either - so it's pretty efficient. Yet it is no longer available in the store, even though it works perfectly fine. However, only a minority who have the technical know-how to access and use a non-store copy of the BAJ installer are going to be able to take advantage of using it.
This would seem to be simply a form of effective censorship by a proprietary gate-keeper who disallows the continued availability of BAJ for the majority - via the "authorised" store - for unstated/specious reasons, and not because BAJ is "no good" either, but probably because it is apparently too good at what it does and could adversely affect incremental advertising revenues for the gatekeeper, or something.
Transparency so opaque you can't see a thing...