They don't assume that. I don't see why people think that NSA is simultaneously genius-level forces of the Illumanti architecting events that will culminate ye

They don't assume that. I don't see why people think that NSA is simultaneously genius-level forces of the Illumanti architecting events that will culminate years later, and yet would make the rookie level mistake of introducing a backdoor that is protected only by obscurity. They know other security services understand how to decompile code (or read the original source). More importantly, they know that critical government services they can't predict will end up possibly running things like their broken version of OpenSSL. There's a FIPS standard, of course, but note that the Heartbleed page made quite clear that FIPS is vulnerable too.