All clients are fully open source, they believe it to be a core requirement for formal verification.
You could make the argument about the play store distributed binary being “unverified”, but that applies to any program that’s distributed in binary form. You never know what additions are made.
FWIW the f-droid version is compiled entirely from source with no binary blobs at all and is still the same client.
You’re not helping anyone by spreading FUD.
They’re literally not. The distributed apps update every couple of weeks or even more often while the source they push lags months behind, if it’s even what’s being used to build those binaries.
I wrote the peertube client Throium which is also available on f-droid [3]. When I Tag a new release on github, f-droid will build the package automatically and publish it the next day. I do not build the packages for f-droid.
[1] https://f-droid.org/en/packages/org.telegram.messenger/
Uncommented code is dumped into the GitHub repo every couple of months after enough people complain. That's not what I would call open source.
[1] https://github.com/overtake/TelegramSwift/commits/master
They're not really all that open.