This implies it's all dropshipped print-on-demand, of course. Which is fine if you're just considering it a donation incentive rather than a worthwhile product in its own right.
Yes, but you might guess they've done some work to find a supplier and test the quality of their supplied products and have a box of T-shirts they know are good. Which they don't - they're basically just plugging your order into a slop fulfilment company. Which is fine if you don't actually care too much about the merch.