Not very professional on Lothian's part. They didn't have to mention any operator and should perhaps have given the customer a link to Traveline Scotland. Sounds to me that some bus operators are getting worse at Customer Services and think that everyone and their dog can do the job.
I suspect it was a genuine mistake. When I briefly worked for First handling enquires in 2011/12, it was company policy not to tell anyone anything about other operators, and I actually got into trouble for doing it.