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.
"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.
If you cross monkbears with owlbears, for 100 offspring, do you get:
23 owlmonks
24 monkbears
22 owlbears
25 (ordinary) bears
2 (demihuman) monks
2 owl (except the owls are not what they seem)
1 bear/monk/owl
1 hen/turtle/dove/partridge/pear, which practices kendo according to the "Book of Five Rings", and when unarmed uses Hen Style savate

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.