The good thing is that these are all separate browser extensions, none of which are bundled by default. So that's exactly the case.
The whole idea behind test pilot stuff is to trial stuff intended for future inclusion in the main distribution, getting it force-fed to be able to claim a large installed base is the logical next step.
Really, Mozilla resource allocation is a mystery to me.
The Vertical Tabs test pilot thing was them demonstrating that it could be done (including to themselves, they need to test these APIs) and giving the community something to work with, should no other tree tab extensions crop up before the deprecation of the old API.
Except that Tab Center wasn't a way for them to test the new WebExt APIs, as it was still based on XUL. See here: https://discourse.mozilla-community.org/t/whats-all-this-abo...
>maintaining [the old extension API] ate up a crap ton of resources, so don't come up with that move being a waste of resources
Arguably not a waste if that meant preserving the most powerful extension environment out there, and also one of the very few reasons for people to stay with Firefox.
Signed: a Firefox user
If the Firefox team wanted to improve speed/security/modularity, etc. they had to ditch the old extension model.
It sucks, but necessary.
Addons based on older APIs could be made compatible with the newer multiprocess design (see https://developer.mozilla.org/en-US/Add-ons/Working_with_mul... ) and for a while Mozilla tried to persuade developers to update theirs (see https://blog.mozilla.org/addons/2016/08/02/multi-process-fir... )
It was only not long after that when Mozilla's fresh direction decided to start pushing the WebExtensions bandwagon only while dropping everything else, in spite of the thousands of man-hours invested by the addon developers (many of which, you can understand, were not happy; see http://fasezero.com/lastnotice.html )
>they had to ditch the old extension model
To me, that's more like a political decision they made at an arbitrary point in time.