Why not to add to the main Portage tree?

[MeisterP]

Upstream only supports building torbrowser with their reproducible build system and not directly from source like I do in the ebuild.
Therefore, I wouldn't move it to the main tree since this evokes the impression, that it is a fully supported package.

hasufell and I actually removed it from the tree after the discussion in https://bugs.gentoo.org/434652
The upstream supported way is to install the torbrowser bundle with www-client/torbrowser-launcher. Everything else is experimental and doesn't guarantee users privacy and security.

Then there was an effort from a gentoo developer in https://forums.gentoo.org/viewtopic-t-1082722.html not sure why it didn't workout.