I was at a party many moons ago and had been accepted onto a PGCE. I got talking to a woman who was about 15 years my senior and she was talking about how she was a teacher. She was dropping it into the conversation left right and centre, and in my excitement I told her I would very soon be starting my PGCE and where did she train? She looked horrified, then stuttered and named a governing body that I know for a fact does not train teachers. I was really surprised and even though I instantly knew it was a lie, I involuntarily exclaimed '[xxxx] trains teachers?' and she literally made her excuses and could not get out of there fast enough. I don't want to say what her original response was as its a bit outing, but imagine sometime saying they trained to be a personal trainer in Sports Direct or a midwife in Mothercare. I thought, if you're going to lie, at least get your back story straight.
Edited to add: this teacher was in fact a teaching assistant at a local school, as I discovered.
I do agree that TAs teach, and spend a lot of their time doing so. The TAs in my school are worth their weight in gold and would be more than able to step into my shoes if I was absent, and are actually more skilled and knowledgeable than some qualified teachers I've worked with. However the training to be a teacher is very rigorous and the responsibility ultimately falls on the teacher, often necessitating a great deal of work during the weekends and in the evenings. For this reason, I do think that there is kind of a gravitas that the role carries which embodies more than just the act of teaching.
If a TA or cover supervisor is, in good faith, using the word 'teacher' to represent the main facet of the role which they feel they fulfil, I guess it's fair enough. However it's just disingenuous for anyone to deliberately use any kind of term which would mislead people into thinking that someone has gone through years of education and training that they haven't.