Who ever said eight would work for Ben? I've said most programs play eight. I have said most programs are now likely to have 10 good, quality scholarship basketball players, not 13. There is not a need to add 2-3 additional scholarship players just to add them or as some sort of insurance. I believe for a number of reasons. Leave a spot or two open is important in a transfer portal world. It is hard to get practice time in during the season, so it is best to only have to worry about ten guys practicing. You just simply don't want 3 scholarship guys on the roster rotting away, not even practicing.
If having 10 good, Big Ten caliber players on the roster isn't enough depth, so be it. Then, you haven't recruited a high enough level to win. In today's day and age, it is nearly impossible to have any difference makers at the end of bench that could just pop in and play if you suffer a few injuries.
You have ten good ones, three get injured/COVID, whatever, you still have 7 that are playing. Any more injuries or issues than that, and you aren't winning anything important anyway (Michigan State, Ohio State, etc included).