Thanks for trying. I found this info on wikipedia that might explain it for me. Some quotes:
"Before automation, calls to a disconnected or non-working number would be diverted to an intercept operator. The operator would ask what number the subscriber was attempting to call, determine the reason for the intercept and relay the information to the calling party.
[1]
The first automatic intercept systems used rotating magnetic drums containing multiple recorded phrases, with a
computer or mechanical control system playing phrases in the proper sequence. Initially, the caller was given the option to remain on the line for a live operator after the announcement was completed; this has now been removed."
Read more:
Intercept message - Wikipedia
There seem to be quite a few variances in what is heard as a disconnect message depending on location and these changed over the years with technology changes. I'm not sure it's cleared up anything for me but I guess I will leave it at that.