I suffer from the same problem. If I go back to my readings before 1.01, they are at 10 minute intervals as Apple specified they would be. The only time they're not is when I'm in workout mode, which is a constant reading.
Now they are at least an hour apart when not in workout, and often times longer than that. It is very frustrating.
And I really doubt this was battery optimization. If anything, my watch actually uses a bit more juice than before. On watch 1.0, with a workout of 30-60 minutes, I'd have around 40% remaining after being worn for 14 hours. Now it's more like 30%. Not a super big deal, but what doesn't make sense to me is that I'd expect the battery life to be better given the watch is clearly not reading HR as often. Go figure.