It might loosen them and might rot the floor.
Gap between floor and wall tiles.
Never fill this gap with grout because tile grout is not flexible.
There is a gap of say 5mm to 8mm give or take high between where the floor tiles meet the wall tiles in the bathroom.
For smaller tiles is advisable to use small spacers.
Place them between the tiles are you lay each one and grout straight over the top.
I m guessing its the thickness of the dot and dab then plaster board then tile adhesive then tile.
The large format 18 inch tiles should have inch space in between.
Fill gaps larger than 1 8 inch.
It shows how to seal a gap in the corner where the tile floor.
Gap between floor tiles and wall tiles.
Caulking is the best choice for this application.
The gap goes 3 5cm to 4cm back to the breeze block.
If your gap is smaller than 1 8 inch in width use regular caulk.
Gently spread the tiles and place two spacers between them one at the top edge of the seam and one at the bottom edge.
To read the rest of the thread look here.
Gently push the tiles together so the spacers are tight in the joint.
These can be left in place and will not be seen when you have completed your tiling.
Not filling the gap can allow water to migrate undeneath the tiles.
The d i y video how to seal a big gap between tile floor and tile wall in a bathroom or shower.
If you have tile on the wall adjoining the tub select a caulk that matches the color of the grout.