There are some things that aren’t limited by the total number of scholarships or the percentage. Equipment is not limited. A team can supply shoes, cleats, sticks, clothing to the team. If a team has 10 scholarships but splits them among 30 players, all 30 can get cleats. The athlete who only has a 50% scholarship doesn’t just get one shoe, and doesn’t have to pay for half the cost of the pair, doesn’t get transportation to a game but not back. The stipend could be considered an ‘item’ provided to athletes, just like cleats, and it is just as true that a 50% scholarship player needs 100% of a pair of cleats as it is that a partial scholarship student needs 100% of the COA. The things provided to athletes are not cheap. I’d estimate my daughter gets about $1000 in shoes ($50), cleats ($150), stick ($100+), clothing ($500) and other things (backpack, towels, tape tape and more tape) before team costs like travel, food, medical care, uniforms are even considered. The coach does have a budget and must consider this, so even though the coach may want to split a scholarship 3 ways rather than 2, the coach has to consider other ways that 3-way split will cost the team - extra lodging costs, $1000 for individual ‘set up’, more uniforms, more food, more coaching. The stipend could be like that too, considered a cost of adding another player, another $3000 or so to the budget (although more likely a cost to the athletic department than the individual team, the AD could start reducing the size of the teams)
I can’t find it in the NCAA requirements announcements about the stipends that it is tied to the number of scholarships or any specific amount. It says that the Power 5 and any other conference that wants to can give a stipend to a scholarship athlete to cover the COA. It doesn’t instruct the conferences/schools how to determine the COA (although some federal guidelines do) or that the stipends must be given at all, who gets what, or limits. If the stipend is treated separately from the scholarship everyone could give the full amount to every athlete, just like a pair of cleats or a stick. I don’t think any school is going to give every athlete the full amount because of budgets, but I believe they could and still be in compliance.