Shift drainage in the shower area

We have 60x60cm tiles in the bathroom and 10x10cm tiles under the shower area due to slipping hazard

That should really be checked carefully. I have encountered shower tile areas in several hotels with tiles ranging from 30x60 to 60x60, which personally seemed too smooth and too dangerous to me.
I have mosaic tiles in my shower area myself, but also very soft water and no problems with lime scale, etc. However, they are always nice and grippy for bare feet.

which were personally too smooth and too dangerous for me.

also for us, despite soft water

We are quite satisfied with our 30x60 in the shower. Hard water. We push the remaining water off once after showering and, of course, also in the shower when mopping the floor. But I also know other showers with large tiles that were very slippery.

It could be because the size of the tiles has absolutely nothing to do with slip resistance. On a 60x60 R13 tile, you're more likely to scrape off your calluses than to slip, whereas with a 10x10 R9 tile, it's better to install 2 grab bars in the shower.

However, walking barefoot is rather uncomfortable on R12 and higher.

That is not correct. Due to the many joints, mosaic tiles do not have a continuous water film and are therefore significantly more slip-resistant. Even if the tile surface has the same value in the laboratory as a large tile

That is not correct. Due to the many joints, mosaic tiles do not have a continuous water film and are therefore significantly more slip-resistant. Even if the tile surface has the same value in the lab as a large tile

But who would want many joints in the shower? Lime, soap, and skin residues really settle nicely there. I would never want to have mosaic tiles.