Oh, this is amazing. Never made sth. like this before. It does not even hit once. (Edited post to not flood this thread.)
Test 1) 43.04 fort, feather wood, dwarf. Massive dodge gain in dwarf, attributes accordingly. (No precise monitoring.)
Test 2) 40.19 fort, tunnel tube, voracious cave crowlers. (Monitored with DwarfTherapist) Massive attribute gain. 400 each in agility, toughness, endurance (only see bodily attributes in animal) in about 5 days. 0 strength, however.
I.e. even a 20 yr. very rusty cave crawler is in top shape after 2 weeks dodging minecarts. A month should, as you say, secure maximised attributes in virtually all circumstances. Ok, basically this is just confirming you, but well, I was surprised.
As I was at it I looked into swimming as well.
Test 3) 40.19 fort, meditative swimming cell (stand around in 4/7 water without moving), voracious cave crawler. No effect whatsoever. (This is the most efficient swimming scheme in dwarves, I just don't use it because of micromanagement requirements.) I hope voracious cave crawlers are not innate swimmers.
Test 4) 40.19 fort, meditative swimming cell with too much water, voracious cave crawler. I had no setups for 5, 6 water ready, but while drowning it did significantly train endurance and toughness (10 each). I.e. it should be possible to train endurance and toughness with a sufficiently fast wave repeater with 1 or 2 tiles 6 and a bunch of 7 water depth. Or a "shower" setup. Utility would be limited though as the minecart dodging works all around better and without risk.
Musing about swimming: It might be that different animals require different depth for normal swimming. Needs testing. Or swimming does not exert animals at all.
Test 5) 40.19 fort, dropping strawberry seeds on young cave crawler. Crushed to death.