Need help working through a common issue for my clients

I coach parents of children with Autism, and one of the primary things I teach is using reinforcements to get a desired behavior we want from their kiddos. Because kids with ASD have repetitive processes towards things they like, parents get stuck in thinking 2 things:

#1 – They become blocked to believing there is anything other than this one thing that will motivate their child
#2 – They are super resistant to taking the one thing away and using it as a reinforcement for a desired behavior (most parents say this is IPAD time)
– This one thing serves many things for these parents:
a) it can give their children a distraction that lets them buffer or have time they don’t have to entertain the child
b) they might feel that taking away the child’s 1 favorite is a punishment because the child really loves this one thing…nothing else (in their mind) and I’m making them feel pain by removing it

I don’t see it this way. I am also an ASD mom and by experience – when I do take this one thing away, it causes some discomfort for all, but I choose to sit with it and it eventually passes.

I’m just trying to see if there is something I am missing here as to why parents are just like HELL NO when I tell them to take the thing and make it a reinforcer. Any advice is appreciated.