But that said, 'SOP' is s just a term, without any definitive definition

. And it can mean whatever people determine it to mean. I dislike both terms (SOP, WI) and never use them, but I do understand they have wide currency in yer typical manufacturing company.
I don't disagree, but I'd much rather see them listed the other way around:
1. The organisation identifies a need (eg, to provide guidance, achieve consistency, set out a preferred way something is to be done etc), or
2. They are required by a Standard, regulation etc.
Might sound petty, but it might help put the focus where it's important and avoid that tired old misunderstanding of 'you only need 6 procedures for 9001'