If you happen to have any kind of Twitter presence, I’d be interested to get your opinion on this topic.
I would want to only change every 4th. I would want to be able to maximize my feats or ability point gains. If I changed every 5 levels I would miss a chance to grow as a character. Not a deal breaker, lol who am I kidding. I DM most of the time. Looking back over my 5E play time I’m not sure I have progressed a character past 10th level. In short the rule would not bother me as a player.
I’m with ya on this in that the PCs in the 5e games/campaigns I’ve run only get up to like 10th or 12th tops and then it’s ended and we move on to the next campaign.
However, now that I think of this, knowing that my players’ PCs only get to 10th-ish, then if I were to limit the multiclass option to only be by tier they might get cranky with me as they’d see it as basically removing an option.