Yes. I know. However those places also aren't aggressive about upgrading their Erlang versions unless there's a critical patch, and even then sometimes those

Yes. I know. However those places also aren't aggressive about upgrading their Erlang versions unless there's a critical patch, and even then sometimes those are back-ported by the places creating, maintaining, and deploying their Erlang systems/software (such as one of my previous employers). Additionally, these changes are largely superficial, not functional. They're in the "make it pretty" part of the "first make it work, then make it pretty, then make it fast" ethos. It's purely developer experience focused of course. The machine doesn't care what order the arguments are in. Well that may not be entirely true. I'd have to look more closely at the function-head matching implementation to see if there's some benefit or hinderance in putting non-scalar types first in the argument list... but that would be in the "make it fast" part that comes later ;-)