Probably not good and a good thing you're taking note of it.
To me that's a sign that it's at that too hot point. Though it might depend what it's wrapped in, or what it's next to that might be overheating.
So I had no idea if that is normal or not.
The interesting thing about resistor wire. It's a smaller conductor, made purposefully longer than needed. Both to create more resistance.
Then it's expected to heat up, as heat is a result of resistance, AND resistance is a result of heat in most cases at least with common wiring.
A good example of a resistor wire would be a pair of 100' long 16ga extension cords trying to power a refrigerator!;D
The PO had it wrapped up along with the main wiring loom under the dash and then had it put in the plastic wiring loom. It sounds like it should be by itself and not all wrapped into the other main loom?
Correct for the most part. All of the ones I've seen through the model years were separate and wrapped in a heat resistant protective sleeve, but then doubled over (it's longer than most other wires would need to be) and then taped to one of the main harness trunks.
So while it's usually at least partially visible and outside the main harness wrap tape, it's still wrapped up with the other wires with some tape too. Probably some heat resistant tape at that.
I've never seen one in plastic split loom that was not a re-wire job by a PO. Even though they have high-temp split loom, I'm not sure what it's rating is and if it's ok to use it. I always buy that tar-coated fiber tubular loom specifically for high-temp conditions. You see it near engines and such, like around starter cables that tend to get close to the exhaust system components.
Paul