Correct. Telco wiring is NOT twisted-pair. The first four colors were the standard, at least for residential wiring.
Well, at least the old station wire or JK wire wasn't twisted pair.
When I started playing with phones, the lines had three wires. I think the yellow carried ring voltage.
But two-wire lines became the standard, and the yellow and black became the LV lighted-dial supply.
The yellow was ground on those systems that used it for one side of the ringer such as for a party line. If needed, up to four customers' phones could be rung independently sharing the same two outside wires. Of course, they could only have one conversation at a time.
Since the old red/green/black/yellow station wire wasn't twisted pair, it caused a problem when customers started wanting two lines. The yellow/black was intended to power the dial lights on phones like the Princess off a plug-in transformer (that sometimes would burn up). It was not intended to be another talk path and when used that way caused crosstalk between the two lines. This is when two, three and four twisted pair cables began replacing the old JK. These twisted pair cables followed the color coding of pairs 1-4 of the existing 25 pair standard.
Originally, the four pair wasn't categized because it was only for voice, but later somebody decided to put data on that cable and ethernet and the CAT2 spec was introduced.
-Hal