how is it not working, mine works normally, have u changed the pixel per unit to 16 ?
oh it is about the custom physics shape, u can look it up in unity documentation, it is in the sprite editor, it helps you create collision (when used with tilemap collider) based on the shape you set
to your question, u can set the custom physics shape of the grass tile to nothing, so that those grass tiles won't have any collisions
