We have an active problem with importers modifying 'timeCreated' timestamp in asset meta files when called from script, see case 856344. It seems though that the Texture Importer rewrite made the problem even worse for textures alone - the timestamp gets updated even if no actual changes are made to the texture. This is a regression from 5.4.

Repro: The parent case contains menu item scripts to quickly see the behaviour in the editor.