I misread your post, sorry. I'm pretty certain the following is happening (from memory, haven't checked) Assuming you're not using dynamic material layering in Painter you have a fixed texel density and the uv scale parameter simply shrinks your material to make it tile more often. In designer the tiling parameter affects…
The texture resolution isn't necessarily different, however the texel density is. It's a big problem when it's super obvious like that. Something placed on the side of the hallways.
There is no point in leaving no space...you should always leave some pixels spacing...the point of leaving as little space as possible is maximizing the texel density.