Let’s say you first import a texture with a resolution of 256x256. Then you realize you could get away with a smaller texture, say 32x32. So you change the texture size, and then reimport it in playcanvas. You’ll notice that the new texture has in fact been imported, but the resolution is still 256x256. What has happened is that the newly imported texture has been scaled up to fit the original sized texture.
The only way to get the correct resolution is to completely remove the old texture, then import the new one. This is far from ideal however, since any references to the original texture will be broken.
Try it out for yourselves:
Link to textures