Lets have a closer look at the maths involved.
You have an image of size 256 * 256, since numbering starts with 0 these are pixels numbered 0 to 255 in both directions.
Now suppose we have 16 tiles in a four by four grid. The bottom leftmost tile will contain pixels 0 to 63 from left to right, the next tile pixels 63 to 127 from left to right. Similarly for pixels from the bottom to the top of each tile. As in diagram below.
That means if we want to take the bottom left 1/16th of the texture
the uv values will be (0 / 255, 0 / 255, 63 / 255, 63 / 255)
and for the bottom right tile the uv values will be (192 / 255, 0 / 255, 255 / 255, 63 / 255)
This method is used for all the tiles in this PG Babylon.js Playground
However if we just think of the tile uvs been split into 0 to 64, 64 to 128, 128, 192, 192 to 256 and use
bottom left uvs (0 / 256, 0 / 256, 64 / 256, 64 / 256)
and for the bottom right tile uvs (192 / 255, 0 / 255, 256 / 256, 64 / 256) and similarly for the other tiles
then we get a PG https://www.babylonjs-playground.com/#584DNF#1 where some borders of some tiles are of the opposite colour. Placing such tiles together will produce artifacts
compared to using 0 to 63 etc
