well assembly is technically "source code" and can be 1:1 translated to and from binary, excluding "syntactic sugar" stuff like macros and labels added on top.
By excluded he means macro assemblers which in my mind do qualify as an actual langauge as they have more complicated syntax than instruction arg1, arg2 ...
The code is produced by the compiler but they are not the original source. To qualify as source code it needs to be in the original language it was written in and a one for one copy. Calling compiler produced assembly source code is wrong as it isn't what the author wrote and their could be many versions of it depending on architecture.
Having access to the source code actually makes reading machine code easier, so you're also wrong on this entirely different thing you're going on about.
I didn't say it was. I just said loosely what the OG meme said, if you know how to read assembly, you know how to read (and write) what some of the code does.