Regardless of if Bill Watterson's take was actually accurately describing a real phenomenon or not, I think its of note that that's what he thought his comic was worth as a piece of culture, human expression and the connection he thought it could make with people. Also not only his comic , but what he thought comics should (or at least could) be.

On the other hand it's 2023 and people can write entire essays about how much a franchise means to them and then go out a buy a funko pop of one the characters and those fucking things are artistically at the level of a post-it note with a crude face and the characters name written on it.

I think evidence in favor of Bill Watterson's point is despite him not merchandizing Calvin & Hobbes, the "Calvin pissing on X" window decals have proliferated and their ubiquity has shaped how people view the character.

Calvin never did that! That's not a thing that he does! That's not a type of thing that he does! It's a different flavor of mischief. It should strike people as incoherent with his character. Yet by and large it doesn't seem out-of-place because the image has basically been accepted as "canon" and the concept of the character has been stretched to include it.