Alright, I tested this successfully and replicated it over the course of a week.
If I set my watch to exercise mode - Outdoor Walk - I have to jog for it to count any of the exercise minutes.
HOWEVER - If I do not have an exercise mode active and I do a walk at a good effort? Every minute counts as exercise minutes. Every single time.
I think this is because from day 1, when I got my first Apple Watch, I used Outdoor Walk to jog/walk (because I couldn't run a mile non-stop like I can now). This trained my Apple Watch that my "outdoor walk" exercise was really mostly jogging and some walking over the many years. I still do this today when I want to have a light jog - I'll choose outdoor walk and jog/walk.
So now, when I want a walk to count as exercise, I just leave my watch in normal mode and go walking and EVERY minute counts. Doesn't count as exercise but it helps with this months' goal of closing my rings every day, lol.
I definitely blame myself for this based on how I treated Outdoor Walks (as runs).