Since you asked and it’s raining... Yes, He is seeing pitches that are quite different.
I looked up the percentages of pitches each player is getting inside the strike zone. I set the limit at an arbitrary 140 Plate appearances. Ranking (by lowest rate) in parentheses:
Trout 43.6% of pitches in zone (143/233)
Betts 42.9% (126/233)
Freeman 41.3 % (66/233)
Altuve 41.0 % (52/233)
Harper 38.2 % (9/233)
And the range for all 233 batters was 37-48%. So Harper is low and the difference between him and the others is significant.
Take out IBBs and run the numbers again....or just run them now with current PAs. Would be willing to bet the difference would be much smaller, and you probably shouldn't include batters from the AL.
Regardless, pitchers may be pitching him differently(as in out of the zone) because they know it works, thats still on him. It would be stupid for catchers/pitchers to not change their approach for each batter based on scouting reports.
Either way, its pretty stupid at this point to not have Soto hitting behind Harper, get him some protection and I bet pitchers won't be so content to just walk him. Especially against LHP, even though I imagine Soto's splits against RHP are still better than Rendon's.