I see no way for this request to be taken seriously by Larian. This is not a Cyberpunk 2077 like failure, where investors were lied to, console versions were hidden from the public until release, so on. The rules for playing an early version of BG3 have been so clearly laid out since the beginning, the whole "not a finished product" thing.
And I have a feeling doing this would open another can of worms, there would be people complaning things like "I only played three hours, I should get a 90% refund, why should I get the same 50% refund as players who went through 30 hours!!"