In many episodes when COLUMBO requests the presence of the killer,
he has already solved the case and has the proof e.g. ETUDE IN BLACK., GREENHOUSE JUNGLE.
So, when he pulled her off the boat it would seem he had the convicting evidence.
Otherwise, he had no legal right to prevent her from travelling.
Ya see my point?
When he pulled her off the boat, he had her in the lie about the keys not being by the bush as she claimed.
But, he solved the case in real time which is unique to the case.
For example in PLAYBACK he had already detected the invitation before he showed it to Werner
Yes, I agree that he solved the case in real time.