I think the rule is similar to like an interception and you fumble it and offense recovers. It’s a change of possession and 1st down even if you don’t reach the line to gain. Same for a fumble lost and defense fumbled it back.
Thats how this rule is interpreted. Once the defense blocks the punt if it goes beyond the LOS and they touch it’s considered a change of possession.
My guess is it happens so rarely Special Teams coaches aren’t coaching it. Didn’t look like we were even aware of the rule while Denver appeared to be.