Earlier quoted context omitted.
Trying to make sense of it, I believe that means Parler was delegating their email verification and 2fa checks to Twillio. And somehow, without access to Twillio's API, they defaulted to not do any check at all? I'm not sure what to do of this, that doesn't sound that realistic but who knows.
That, or Twillio was reporting authenticated emails, without actually authenticating them? It seems to involve some skipped auth steps on someones part though, not just a fail-safe/fail-dead mixup. It's not clear.
Instead of having "if explicitly ok, proceed", they maybe had "unless it's an explicit negative response in an expected format (or a connectivity issue, timeout, etc.), proceed"?
Which would be a pretty dumb thing to do, but I've seen worse.