This was already noted by Horn here: https://discord.com/channels/1116389027176787968/1321000109449941013
However, this doesn't just cheese unlock requirements - if the vouchers change a value by a numerical amount, they get reapplied several times. In the screenshot, there are 5 slots in the shop because I bought Overstock several times in a row, and I have 7 discards because I bought Wasteful three times in a row. Non-numerical vouchers apparently do not do anything if purchased additional times.