I'm not pretending to be an expert - I've just tiled a few walls and on my second floor. But, whatever I'm doing, I always read up on, and follow the experts' and pros' best practice - not where the latter are just saving time or cutting corners, but definitely when they are avoiding call-backs and potential issues. One of the joys of DIY is being able to make sure the the job is done right. I'm happy to follow those with much more expertise on stuff like this, especially when the hassle and cost of it going wrong fars outweighs what little saving is on offer by using tub gear. Try ringing a BAL, Ardex, Mapei, etc tech help-line and see what they say re large format porcelain on plasterboard. The non-setting picture frame story is from pro tilers who have experienced it with problem installs (and not overnight, weeks later).
Well, I've been DIY tiling for more years than I care to remember. I have used just about every size of ceramic wall tile going, and have always used ready mixed tub based adhesives. I have, over the years also had cause to remove tiles previously fixed in this way, and have never seen your picture frame effect. In fact I usually have to smash any tiles off with a hammer and chisel. Up until now, my tile adhesive of choice has been B&Q Cerafix non slip, which I have found to be an excellent product.
I actually object to you suggesting that I am any kind of bodger who has "incorrectly used a product a few times and got away with it", and just plunges ahead without doing any kind of research. If you have "done a few walls" then I would suggest that I have probably done an awful lot more tiling in my life than you.
The outlet that I used to purchase my current large format tiles, is a small family firm, and the guy that runs my local branch is very knowledgable about the range of products that he stocks, which is why I am prepared to listen to him, and any advice that he has to give. He has a number of different adhesives in stock, including mix it yourself types, but the one he recommended for fixing these tiles was a heavy duty non slip tub based one. That was good enough for me. He's hardly going to recommend something that will allow the tiles he's sold me, to fall off the wall, is he ?