As someone who takes kids to speech therapists, it is not the same. Casual conversation is critical to help correct speech impediments, that practice with a therapist alone would not give.
He could be seeing a speech therapist in too, but one is giving him technique and exercise in how to improve and the other is helping him get practice.
I used to work in the Apple Store. It was quite common for people to come in, hand me a card that said something like “I’m practicing my speech, please be patient”. Was pretty wholesome
Ignoring the context of this thread, I'd like to imagine that they busted out a rousing, inspiring, pre-rehearsed speech, and everyone in the Apple store clapped.
Not just that, but sometimes you just want to feel fucking normal. Going out and talking to someone is something that was beyond his grasp. Paying an escort for a conversation at a restaurant gives a veneer of normalcy that you can't get from a speech therapist.
I would imagine, having the speech therapist there would make it seem more like a counselling session. With the escort, you can look past that aspect and settle on it being a normal conversation.