I'm going to take a wild guess and say you started off doing plastering/rendering first right Craig?
I find it hard to take criticism like the argument you so succinctly put together from someone whose website has photos showing them skimming walls that are going to be in a wet area of the bathroom, i.e. around a shower in a bath. You couldn't put a worse substrate in a wet area really if you tried to. Also, if you have tanked those walls then it certainly doesn't look like it from the photos. But no worries, that will be another bathroom shower area getting redone in 4 or 5 years time when black mould and wet patches start to come through the wall. It certainly doesn't look like it's been installed by someone with a good understanding of substrates and tanking methods to be honest.
And you say I don't have a clue right?
But then I presume you wouldn't bother to tank the walls if you are using ready mixed adhesives, because they don't set properly on tanked walls either. The only benefits ready mixed adhesives offer over cement based adhesives are they require less preparation time and they are easier to apply. They are in every other way totally inferior to their equivalent cement based adhesive products. These reasons make them much more suited to the DIY market than the professional tradesperson.
I'm sorry if you didn't like me stating my opinion and I do appreciate it may sound harsh but in my experience professional tilers do not use ready mixed adhesives and I stand by the comments I made earlier.