Mmm I see I see...
Ok, the problem is that many objects are not designed to have a square collission box, since the Rpg Maker is the only software that forces that . I can try to shift every object that doesn't touch the bottom of the tile so the RPG Maker character can interact with them without being distant. For the bathtub example, I have no idea why the animation of te bathrtub works the way you mentioned since it's the sprites are placed in the same way on the grid, that's weird. Down scaling breaks proportions and require a lot of time, so I won't do that.
Also, I'm gonna add a suggested plugin on the asset page, since there are some out there that rewrite the collission system of the RPG Maker, and even the step length of the character, meaning that every now mentioned issue would be fixed.
I found this plugin for the MZ that allows you to set a custom character step length! The MZ is fairly new, but I'm sure in the next few months some useful collision plugin will come out!
Love the tenacity, just wanted to share that the MZ plugin doesn't really work that well and I just had a chat with the creator who said he doesn't recommend using it. So I think maybe remove that recommendation so it doesn't fall back on you for recommending it ;) Keep up the good work, always happy to see what improvements you come up with.