Yes and no. Of course a player will be more "physically ready" as 23 year old senior vs. when they were a freshman, but don't you get more physically ready when basketball is your profession? Access to world class trainers, facilities, dietitians, etc. There are literally Olympic athletes in the NBA vs. only allowed so many hours/practices in college. I don't think Malachi has an NBA body now, 4 years later, so I doubt he'd have one by the end of his hypothetical sophomore season.
I mentioned this before but it's worth repeating - staying in school is 2-sided risk. Every year you stay in college and show your physical growth and basketball development, is one year that NBA scouts don't have to guess and project. Both your upside and downside change - your range (ceiling/floor) converges.
Players improve their draft status to the extent they "exceed" expectations for development. If Malachi was a projected late 1st round pick as a freshman, but returned as a sophomore and was expected to score 18 ppg, and he did that, why would a team draft him higher? If he went crazy and scored 23 ppg in the ACC, he'd be picked higher. If he scored 13 ppg like he did as a freshman, he'd drop, likely into the second round a.k.a. NBA purgatory.