Yes, it's reasonable to expect that everyone either shoots the same or improves. No homerism in that logic. Good talk.
That's certainly been the case at Purdue more often than not the last several years, particularly guys from their 1st year to their 2nd. There are exceptions (Carsen last year) but they are often attributed to legit reasons (he played a big chunk of the Big Ten season with a back issue).
Plus, drops in percentage usually equate to a few makes over the course of an entire season. Wheeler and Boudreaux have dropped like a rock.
Here are the percentages by year for the last 8 Purdue players who completed their eligibility or went pro early:
Carsen Edwards - 34.0%, 40.6%, 35.5%
Ryan Cline - 38.5%, 41.3%, 39.6%, 41.7%
Vince Edwards - 32.6%, 40.7%, 42.3%, 39.8%
Dakota Mathias - 32.2%, 38.6%, 45.3%, 46.6%
PJ Thompson - 28.6%, 41.5%, 40.2%, 44.1%
Caleb Swanigan - 29.2%, 44.7%
Raphael Davis - 30.3%, 27.3%, 30.0%, 35.5%
Terone Johnson - 29.3%, 31.0%, 34.6%, 35.2%
Only Davis didn't improve from Freshman to sophomore year and it was a single miss on the same number of attempts.
It's strange how you search for things to challenge people on.