Not much you can do - if the machines decide you don't get a refund, well, then you don't. I haven't bought anything on Steam since.
0. https://www.accc.gov.au/consumers/consumer-rights-guarantees...
Ironically because speed-running requires a lot of practice this often means purchasing two copies of the game - the first to practice with, and the second to be (potentially) refunded!
There should be some sliding scale where you can make a great 2 hour or less game without the risk of infinite refunding (perhaps the game could be marked with a "half-way" point, etc, though that would involve the shop actually playing it).
I bought 2 copies of a game advertising co-op to play with a friend, only to discover it's local-only. (Steam didn't have separate "local/remote play/online co-op" labels yet) I opened a ticket and they refunded me as a "one time exception".
The usual refund conditions are “less than two hours of play, within two weeks of purchase.”