I understand, and what you shared is a perfect example of what I said- but I fundamentally disagree with the notion that it's the same between the two.

I think that in effect, as you associate more behavior with a particular struct(as opposed to what you're attempting to do with said struct), the greater expectation it presents that the struct is what you code around. More and more gets added to state over time, and more expectations about behavior get added that don't need to exist.

Sure, you could say "Well, then just be strict about what behavior is expected in the interface"- but that effort wouldn't be necessary if we didn't make the struct the center of the behavior in the first place.