A league buys differently from a club because it is not buying for itself. It is setting a standard that many clubs then order against, and its problem is enforcement rather than selection.
The usual failure is that each club orders from its own supplier, the competition rules get interpreted differently, and by round three there are three different number heights and a shirt that does not meet the sponsor regulations. The league then has to police it retrospectively.
An official supplier arrangement solves it at source. We hold one league template — number sizing, sponsor zones, competition marks — and every club orders their colourway against it. The rules are built into the artwork rather than checked afterwards.