If you become accomplished at moving your human body to anticipate blows and move in implausible ways, can you still do that in the body of a bear?
My answer is no, that wouldn't fly in my game. The ursine body does not lend itself to martial arts. Your muscle memory would be working against you at every turn, and there are motions which the human body can perform which are just physically impossible for a bear. The very idea of a bear using martial arts is ridiculous.
On one hand, it's time to fund studies on the topic, and see if it can be accomplished and replicated.
On another hand, anyone who has learned boxing, and then learned karate, or vice versa, has learned one set of ways to punch, and then another set of ways, similar but subtly and significantly different. "Jeet bruin do" is an opportune pun; it's also 100% on the money, because jeet kun do is (among other things) the skill of managing multiple sets of martial arts muscle memories.
So if you can show me that multiple sets of muscle memory prevented Bruce Li from being an effective martial artist, then my table won't allow druid/monks to spend two hours each downtime day, practicing their moves in bear form, and developing two sets of muscle memory, one as (demi)human, the other as bear.
"there are motions which the human body can perform which are just physically impossible for a bear"
Yep, that's why I mentioned rising block, sweeping block, elbow strike, uppercut; and NOT leg sweep, nor snap kick, nor knife hand, nor anything from the holds-and-throws category. Bears can learn to *pedal bicycles* and to steer bikes by leaning. You might be underestimating what else they can learn.
I prefer to err on the side of NOT underestimating bears when they also have human-level intelligence, but hey, suit yourself; your table follows your rulings.