most of the time when im tiling the tiles are from a bath or shower tray or floor the walls are usually vertical so the pressure of the weight is vertical and the weight is supported on something . I must admit that the majority of my jobs are not onto skimmed walls which we are talking about.
if your concerned about weight you could put a row of L brackets above your tiles mechanically fix them to your walls and hang your tiles on them weight problem solved lol
have used them in the past to support tiles above windows
used to use L brackets when I did slabbing in the past. have a idea any one know a dragon to lend me some money