@bmensch1
As you mentioned, the NBA is a superstar driven league, with the rest of the spots filled with role players and specialists.
Now ask yourself, in his minutes this year, was Bryce Thompson able to showcase his skills in any way that would give an NBA GM a reason to think he has the skillset to fill any of those roles on an NBA team? The answer is clearly NO.
So when you are comparing it to the business world, you see Thompson (or McClung or Grimes, or whoever) as a guy that at their previous school didn't even have the qualifications to apply. They are the equivalent of a resume that doesn't even pass the initial screening to get to the hiring committee.
But by transferring, McClung and Grimes have both gotten opportunities to really show their abilities. Grimes particularly.
You also have to remember that the NBA isn't going to have a lot of guys, particularly role players, that will stay with one team for a long time. Robert Horry, perhaps the greatest role player of his generation, won seven championships with three different teams (and played for four teams, total).
Some of the best role players in the league now have played for 3 or 4 teams already in their career. The Morris twins have each played for multiple teams (Markieff has played for five, Marcus for six).
Most players, especially role players, won't play for just one franchise, so it's doubtful an NBA GM holds attending multiple colleges against them. That may be a benefit, because they have already seen two different systems and coaching staffs.