Yes, the haircut, as you call it, is exactly the failsafe that will keep HBD strong. I think that any algo stablecoin without a similar function is ultimately susceptible to a bank run similar to UST. These exchange protections must be in place. That said, I would like to see some form of regulation over stables further requiring partial pegged currency backing even for algo tokens.
End of the day, over regulation is bad but some regulation is helpful.