I'll go on average....because I didn't time it.
I usually try to start with all my stats at around 30% to get a buffer starting point

Your bow aim faster etc... and btw, I didn't look if bow still upgraded itself for hitting a tree, but this is how archer trained.....well they would hit a haystack target but similar......since we don't have that in the game...

But if i go on average...takes maybe 30min of constant hitting to get to 30%... let's say i downplay it, i'm generous there... you hit 30 times a minute.... so that is about 900 hits to get to 30%...and this does scales so it is harder to level up.... Let's say you kill a mob in about 3 hits, i would have to go on a rampage searching for about 300 mobs to kill and bring some wood with me to build up repair station.... yeah this won't take 30 minutes anymore....this will take the whole day....

I mean if you can craft a dummy as a beginner with proper mats and that said dummy can at least survive.... 50 hits if not 100.....9 dummies....

But back in the days, people would train against people with training weapon indeed....we don't have that in the game...so hitting a tree instead is fine by me

Keep in mind that all the other skills can be trained without involving creature hunting.....
You could argue that blocking requires creature hitting you....yes but you only have to gather a pack of 4-6, make a barn and have them hit you for the next 4 hours to get to 50%... you keep your shield up pressed and backspace in a corner.... yeah i leave something on my keyboard and i'm off doing something else... but can you imagine.... 4 hours of constant blocking ...about once every second.... that is about 15000 blocks to get to 50% only...... i could finish the game 20 times, if not grinding the skill, there is no chance whatsoever that i'll get near 100%