You have to remember a LARGE amount of the time the best OL in high school become LTs in college....and the best of the best OL TYPICALLY become the LTs in college as well. We've seen a little bit of a surge of RTs really being special as well (but again we are talking the overall norms).
That's why many teams, not just GB will target the best OL, which often are LTs to move around. It is grossly easier "normally" to move inside than it is to move a guy outside, but that doesn't mean it is a sure thing. Most guys are shifted to interior OL positions due to a lack of physical traits to succeed on the outside, whether that is quickness with foot work, length in both body type as well as arms and honestly sometimes body composition can too play a factor. Yes, some get moved inside out of need and just excel and stay....others yet to be the brain of the OL (Center) because of need...but again overall most interior OL are there because they cannot succeed outside, while a lot of outise (LT and RT) lineman are there because they're some of the few that can succeed outside where things spread wider, need for quickness is higher and you are facing some of the most athletic guys that exist on the defensive side - you're not a tackle because you cannot succeed inside...