Here I hope to make it easier for people to find an authoritative definition for the meaning of an ISO 8601 profile. To be clear, this doesn't mean the definition itself will be simple or clear. Sorry.
I was able to find the document below by way of this [English Language & Usage StackExchange] post: [What does it mean for RFC 3339 to be “a profile of” ISO 8601?]
You need to read ISO 8601, in particular ISO/WD 8601-2 Annex B, where the term "profile" is defined. It's not a regular English meaning; rather it's tech standards jargon.