I don't disagree with your general analysis, though they had their reasons for not starting him (didn't want him in the field, needed to evaluate Altherr before losing him completely, didn't want Cutch playing CF though eventually they had to do that). It was just folly to think he could be a good bench player without getting any starts but the knew their two corner OFs weren't going to get many days off (just like Hoskins and Realmuto don't).
But Nick Williams and "how best to win games" don't belong in the same sentence. At most the marginal advantage of giving him a PH over anyone else (with or without platoon advantage) is slim to none, and a couple of 0-5 starts from him while playing poor defense isn't going to help anything either.
I'd be more inclined to argue that since the games are meaningless they should give him a couple of starts, but technically they still aren't meaningless (both to us and to our opponents).
We're talking about a guy who had the second-worst WAR on the 2018 team. The worst was Kingery, so yeah, it's too bad Williams wasn't given a chance somewhere else to see if he could find his bat again though obviously if they trusted Williams to play CF he had an opportunity.
Several of the Klentak's biggest mistakes this year resulted from being indecisive/hedging his bets about RF and 3B while the Machado/Harper market played out, even as he was decisive about LF and SS and C.