But it isn't, because the reduction in credit score from the query doesn't necessarily prohibit two simultaneous loans, it just makes the terms worse (and so makes default more likely).

And there are obviously better ways to prevent "double spend," like reporting the new loan being granted, which actually should reduce the credit score due to the new debt. It's not as if we can't make computers capable of updating this information in real time.

The interesting thing I've noticed is that opening a new credit account often doesn't actually get that information on your credit report. It sometimes only shows up after you've made the first payment (either loan or credit card). I wonder if that's why the system dings you for too many hard credit inquiries. I agree with you that there's no reason why this couldn't be fixed, though.

Or rather it discourages people from attempting to apply at multiple places to get the best offer..

Typical rate shopping is not discouraged: https://www.experian.com/blogs/ask-experian/do-multiple-loan...