I think this makes a lot of sense. Height is likely a major reason why guys like Ray Rice and Roger Powell only went as far as good college player and Euro prospect. If Roger had been 6'8" or 6'9", or Ray had been 6'6" or 6'7", their pro prospectus might have been much different.
Roger at 6'9 or Ray at 6'7 would have been no-brainer lottery picks, just like Goodwin would be at 6'8. At 6'4 with his lack of elite level explosiveness, Goodwin is not going to get much of a look as a SG unless he becomes a Buddy Hield like scorer (20+ pts, 40% 3pt shooting to go with his advanced game off the bounce). I wouldn't bet against Goodwin doing that, but shooting is more than just correcting form and getting in reps during summer workouts: if you change your release, you need to get up thousands of shots against game-speed defense to build muscle memory. There are also a hand-eye coordination and depth perception components that are only partially correctable through coaching and repetition.
If he sees himself as a future NBA point guard, I can see SLU being the right fit.