You may be right. Just eyeballing some recent Twins, it looks like Gordon was called up 5 times last year. In 2019, Littell and Smeltzer were both called up 5 times; depending on how they count things, Cave was on the opening day roster and then optioned and recalled 4 times after that. That’s as far as I have looked so far.
But, perhaps an official limit of 5 may cause teams to be a little more judicious with them? Not a huge effect, but even if it’s rare to need 6, teams may try to maximize flexibility by avoiding maxing out at 5 until it’s late enough or absolutely necessary. And knowing that they are being counted, teams may be a little less inclined to “waste” one of the call-ups on a short-term stay? We could see teams spread out their call-ups, especially the short-term ones, a little bit further down the depth chart — for example, 1 of Littell’s 2019 call-ups could have gone to a different pitcher.