Seems to be a serious degree of "groupthink" going on here, categorically stating that spotfixing is dangerous etc is nonsense. Even though your British
Standards frown upon the practice, it definitely has it's place if done correctly (with
cement based adhesive that is - hate that mastic crap)
Now having viewed the photos provided, I would not be happy with that amount of coverage - too little in my opinion. In a perfect situation you wouldn't have to spot fix tiles, however customers aren't always willing to pay to render walls plumb, and rarely are walls truly plumb and flat. When done right the spotting method uses more adhesive than the notched trowel, not less, but means it is easier to plumb the wall (say 8 to 10mm top to bottom) because the blobs should squash out to fill the voids. Think about it this way, if you were to cover the back of the
tile completely with a notched trowel, and every trowelled ridge were to come into contact with the wall, you're probably only getting 55% to 70% total adhesive coverage anyway - you still have the valleys between the ridges. The goal is to eliminate lippage, or plumb a wall that is slightly off, not to save money by using less adhesive.
Now having said the above, I'm not defending the tiler in this particular case - the lack of a membrane in a shower and around the tub area seems pretty daft to me - nor am I saying that one should use a method contrary to your country's standards - I merely point out that the technique has merit and will perform just as well as the notched method, but only if done right.