He's saying that they made a decision, then explained the reason for their decision. That's the best possible way to receive a No as a founder.
I think a comma is missing:
> Almost immediate and right to the point that they wouldn't invest, with specific reasoning/metrics behind them.
I don't think so, I think it says he was really pleased with the rejection (and that could have been because it came with actionable feedback, like reasons and metrics.)
Don't you mean "without specific reasoning/metrics behind them"?