I think awareness of the different neurodiverse path is good and the new trend is probably based on research, and not a whacky new trend with no empirical basis. I'm somewhat against PECS. It's basically about making your child give over a card with a picture of what they want before you will give them what you have ten minutes before being passing them freely: bubbles; a favourite sensory toy. It basically presents communication as something artificial, rather than naturally evolving.
I've sometimes wondered whether, left to evolve conversation naturally, children who experience ASD would use words to try to meet their own needs, initially, and then, over time, use language to start to talk about a special interest, like music. I don't not what is being advocated in place of PECS, but it might be a system which combines some of the 'old ways' of encouraging communication, but simply be more personalised and responsive to the child's own initiatives.
Certainly, children with ASD will make sense of things which interest them. Communication strategies which are too rigid may fail. It is not so much not being able to use language, but more wanting to use language to advance a particular interest, for a lot of ASD children. I think that strategies which are responsive to the ASD child's interests work best. There is a danger that if you force a child to try to do talking in a set way, that you will put them off education and then it takes longer to reconnect them. This is what some Speech and Language specialists cite as the danger of ABA. It probably works well as a therapy for some ASD children, but certainly not all of them, and not much good if it increases their anxiety.
You can't teach a young child with ASD that "This is orange. Say orange". If they get it at all, they might never generalise that understanding to everything orange, but think you mean that felt pen must be labelled orange. In the same way, I think that exploratory play with Montessori type sets for fitting pegs to the number of holes, obviously works better for finding out 'one more is needed' than saying "This is 3 + 2, look, say 3 + 2" , before the child has an understanding of 1:1 correspondence.
As a mother of an adult with autism, I know that you have to give freedom to express thoughts, and to do it during the childhood years, otherwise there is a danger that the individual with ASD will think that communication is a game where you say what the other person wants to hear. The impact on that on the adult, who might later in their life be looked after in some kind of official care setting, is that they won't be able to self-advocate for their own needs. They will think "What happened?" is a statement saying " I am asking you a question, can you remember what you're supposed to say?" - a kind of game again, like PECS, or those endless question and answer sessions they do in special schools, or card games which the ASD teenagers probably don't know the meaning of, nor want to win.
Quite a number of friends whose children have ASD, young adults now, like my son, say that at school, something would happen, like they would ask their son: "What is your favourite meal?" and the teenager would say: chicken pie" and the mum would say, "They never eat chicken pie". It's maybe been suggested before as an option and the person will think: "What am I supposed to say this time?". To work communication strategies gave to cover social expectations, but also evolve with the interests of the child.