I have a co-worker saying that most teams don't use all 85 scholarships.
Exactly - if they have empty scholarships by the start of the season, they will often use them on a senior - that way they do not go unused, but they are also not locked up for multiple years and they can have more to offer freshman/transfers.There could always be unused scholarships, especially when players leave the team during the summer. However, most coaches will use those to reward an older walk-on with a scholarship for a year rather than letting it sit unused for a season.