I could be wrong but, based on the limited documentation, it looks to me like they hold on to the Monero and then send it out when someone claims the voucher. Think of it like a fully centralized second layer (since you can essentially transfer Monero without on chain transactions, even if you have to trust that the admins won't just run with all the Monero from non-spent vouchers). I don't really see the point of this because Monero is already very inexpensive to move on the base layer and you are trusting the admins to never touch the idle Moneros.

Not saying that it can't have any usecases, for example: it would be easy to hand out a bunch of vouchers at events (and these guys are sponsors of this year's Monerokon 😜).