It seems like you're saying there should have been a second gun. I don't necessarily agree or disagree with that. I'm saying there wasn't a second gun.
I misspoke about the compression. You're right, there was an athletes with disabilities start (visually impaired, maybe?) between Corral A and Corral B, and so there was a time gap there between Corral A's final starter and Corral B's first starter. It wasn't 12 minutes, though, and saying Corral B was held back 12 minutes is misleading. They started pretty quickly after the AWD start, which started pretty quickly after Corral A cleared. Corral B started a total of around 12 minutes behind when the first Corral A athletes started. If there had been no gaps surrounding the AWD start, it's likely that would have been 2-4 minutes less than that.
Could Houston change their start sequence next year so they have separate guns for the different waves? Sure, it seems from the outside like it would make sense. But regardless of what may or may not make sense in the future, there was only one gun this year.
You can still make a case that USATF should grant this athlete a waiver, but that the chip/gun differential wasn't large can't be a part of that argument.
(Apologies for this pedantic side conversation, everyone!)