He says OTF he wants to be able to go for stacks OTR, at least some times. However, his sizing in the hand would require a PSB shove OTR, which probably isn't optimal for Villain's response. Which we could ignore, 'cause micros, except his whole argument for betting so small is that this villain is savvy enough to respond appropriately to that size. Seems like he's switching his read mid-flow if he's betting small to exploit villain's awareness, but then shipping large on the river to exploit that villain wont be able to respond appropriately.

This is a decent example of what I said in another thread about sizing your bets OTF and OTT for a river shove being something you don't need to put too much thought into, just bet ~2/3 PSB on each street and you'll be sized OK for a river shove.
In this hand, 3-bet PRE means he can get stacks in with 1/2 PSB's pretty well.

I have only the same advice as before. There's little-to-no benefit to your growth as a poker player in the micros to be looking at when and why to bet smaller than 1/2 PSB. The Villain's against whom this matters are not the majority of the population of fish you should be targeting.
There are so many more important leaks in any micro-stakes player's game to focus on that come up more often and have a greater affect on your bb/100 hands.