Sounds like that's the case to me as well. Having safe stock phrases is explicitly a strategy used by autistic individuals to cope with unexpected situations. Like, one common issue that teachers often run into with more severely autistic students is that they'll say "no" to requests because they need to give a safe response of some sort, and the teacher interprets that as being willfully defiant rather than simply overwhelmed by the current situation and trying to do something safe.

He says exactly that in the post: "Why couldn’t I think of the snappy response? Because I can’t do verbal processing and emotional processing at the same time!!!"