Functionally speaking, that is how it works and always has, although I don't know if they've ever explicitly said that anywhere. It was almost never an issue in the past but with three locations open now and more League members able to purchase and pickup beers, it could happen more frequently.
They have said that in a perfect world, League members would buy up all of the special release beers (far more realistic for bottles than the canned IPAs/kettle sours). They generally make an effort to not publically advertise special releases they expect to sell out during the League sale but sometimes demand shoots far beyond their expectations.