It’s pretty clear what the issue is. Harden is trying to make PG play like Luke Kennard. This is the same issue LeBron had with Dwayne Wade and Bosh.
Links are here: you might have to change to EFG% https://www.pbpstats.com/on-off/nba/player?Season=2023-24&SeasonType=Regular%2BSeason&TeamId=1610612746&PlayerId=201935
It’s like trying to start Lou Williams in 2020 over Pat Bev.
Wait until the playoffs (or pandemic) then he’s like a 41.6 TS% solid don’t matter who on or off, that’s what I call consistency