More like guesswork/assumptions than reality
Sorry to be blunt, but you’re not a developer and it shows. Android’s build system was purpose made to be reproducible. Electron was not.
There is so much going on in an Electron build, most of which is out of Signal’s control unless they maintain an entire fork of the Electron build stack. That is an enormous engineering effort for basically zero benefit.
It probably is functionally reproducible, apart from checksums differing due to build dates baked into the artifacts somewhere. It’s not as easy as you think.
If you think it’s as easy as “building it in a Docker container,” then by all means, try.
The guy you were replying to is saying “People hate GrapheneOS because it requires a Pixel,” they were not saying “everyone in the world should be using a Pixel” as you seem to have mistaken.
You’re getting very fired up and heated in the comments here… maybe take a break?