let's admit that the term was not a "latin" maxim as you imply
If volens isn't an abbreviation of the latin maxim "volenti non fit injuria" [which itself is a handy abbreviation], then it's news to me.

Personally, I have never been much interested in the precise derivation of these abbreviations. They are handy and they work in the company of lawyers and judges and that has always been enough for me. I confess I'm the kind of person who drives a car to work everyday but I've never been curious about what's going on beneath the hood [unless I see smoke].

Nevertheless, your explanation of the actual derivation of "volens" is welcome. I certainly wouldn't want anyone to think "volens" is a latin maxim if it is merely derived from, or inspired by, a latin maxim.