He's not suggesting that Frigate should be discarded sooner. Just pointing out that Frigate and Outpost are 2 cards that stay out not because they do something next turn, but because they aren't done doing something during cleanup of the turn before your next turn.
There was a bunch of discussion/question a couple months ago about whether the Duration rule was "discarded on the last turn they do something" or "don't discard if they have something left to do during cleanup". With most Durations, those 2 rules function identically. Frigate, like Outpost, requires the second version of the rule to function; they are not actually discarded on the last turn that they do something.
Okay, I see.
The rule had actually been
"don't discard in cleanup if it has something left to do" since the beginning. The phrase
"discard on the last turn it does something" is/was in the rulebooks, but was never technically accurate in all cases. (It's even an early ruling that Outpost 1E stayed in play even when it didn't give you an extra turn.) I haven't seen a discussion about that recently.
There was a discussion about Cargo Ship and Garrison though, since they can cause you to do stuff
after clean-up. The rule was then changed to
"don't discard in cleanup if it has something left to do after this turn".