The reason I used the nasm logo is because Assembly itself doesn't have a logo since it's not really one language. This is the one I'm with the most familiar with so that's the one I used. This meme would apply to any Assembly language.

nasm is an assembler though, not a ‘languages’

That's like saying "clang is a compiler though, not a language". It's correct but completely beside the point. Unless you're writing a compiler, "cross platform assembler" is kind of an insane thing to ask for. If want to learn low level programming, pick a platform. If you are trying to write a cross-platform program in assembly, WHY!? Unless you're writing a compiler. But even then, in this day and age using a cross-platform assembler is still kind of an insane way to approach that problem; take a lesson from decades of progress and do what LLVM did: use an intermediate representation.

Are you arguing that assembly languages are not architecture-specific? I don't think that's the typical definition.

Nasm is an assembler, but it also represents a specific assembly language targeting x86 architectures.

Gas is an assembler of a higher order. It can emit code for many architectures, and thus it accepts many different architecture-specific assembly languages.