that's not assembler tho - that's assembly like language translated into actual ISA machine code. And going with AT&T will just annoy people for no good reason (despise what article claims)
And where is the AT&T? Did you even look at the syntax or read the article? Is it just the use of `%rex` to prevent namespace collisions with parameters and constants which could hypothetically be named `rex` (and there could be good reasons they are named that too)? There are no other sigils in the grammar. The order of the operands is Intel-like. The memory operand syntax is Intel-like.