While this is true, I felt like this proposal wasn't so much about reducing load (as shortening cache times seems counterintuitive to this), but rather about removing complexity. That means less room for certificate misissuance (CAA rechecking was broken in the past), less code to maintain, less things that can break. This may be worth much more to LE than minor changes in validation load.
(Of course LE also cannot afford to ignore performance, both sides have to be considered)