this doesn't make sense...

every company that maintenance a code in a sane way, requires any changes to the code to be peer reviewed by their colleagues.

Government will need to know first who to approach with the gag order, secondly there is a high chance the peer reviewer would tell about backdoor code to the boss.

I'm not saying it's impossible to smuggle a backdoor, but it's fuckin difficult, at least the way Durov described it.