Can't agree more. And you didn't mention perhaps the biggest snare: if you have a stud bat at catcher, by whatever means of acquisition, it puts pressure on your roster. Because, if you say "we want that bat in the lineup at DH, even when he's not catching," your manager is going to be constantly begging for some form of third catcher. And you can't attract a top level DH to your team, because he'll know he can't play full time. (In a non-DH league, the problem merely transfers identically to 1B.)
I think "managers might ask for a third catcher" is an exaggerated problem (even Gardy didn't have a 3rd catcher that often), but it doesn't seem to apply here at all. Grandal played some 1B last year, and the Brewers had exactly 1 day of 3 catchers on their roster before September.
And there aren't often "top level DH/1B" on the FA market, at least not ones that separate themselves in value from the next tier at that position. And the White Sox already got arguably the best 2019 FA DH/1B under contract for 2020 (Abreu).