I still don't understand why people who want to learn amd64 assembly won't read x86 tutorial. I write both x86 and amd64 assembly from time to time, and I don't think there are anything that make x86 tutorial/manual not applicable to amd64.
Sure, there are differences: register name, C ABI convention, system calls, memory modes, etc. But those information can be find easily in references. And you need reference for x86 anyway. Otherwise all mechanisms are the same.
It's a bit of a catch-22: you can't know that there's not much different between x86 and x86-64 until you understand both. I guess asm newbies have some kind of mistaken idea that x86 is irrelevant and not worth their time learning (even if it were completely dead in the wild, which it absolutely isn't, you still need to know it truly understand the architecture); I've tried to post older x86 and ARM assembly language guides, much better written and more in-depth than this article (no offense intended to the author), and the only comments I get are along the lines of "this is old, it doesn't even cover x86-64/ARM64."
With so many other things to learn and ideas to implement, something like assembly programming sits way back on the backburner. It's only recreational for me, not something critical for my work.
An easy tutorial like this injects just the right amount of motivation to atleast dip my feet back in. Having to wade through Intel's 1000 page system manuals to check if my past knowledge is useful or not, would require a lot more motivation than I can muster.
For experienced programmer this is most certainly true. If you are just starting however it is much easier if tutorial uses the same platform you are targeting.
Sure, there are differences: register name, C ABI convention, system calls, memory modes, etc. But those information can be find easily in references. And you need reference for x86 anyway. Otherwise all mechanisms are the same.