Not really.
Granted, I'd also not rely entirely upon the DRB, or other computer scanner/interrogator, since it's going to get its information from the same place your gage will (coolant temperature sender.) Use a non-contact infrared thermometer to backcheck the gage instead, since it will give you a reading on the same system with a totally different source (no point in back-checking a gage using the same sensor that drives the gage - that's why I tell people to check their oil pressure, when suspect, using a mechanical testing gage.)
It's possible you've just got a cool runner - I've got an 88 that DOES NOT LIKE having a thermostat. I put one in, it overheats. I don't put on in, and it runs just fine. I don't understand it, I don't know why, and it's the oddball (out of the five I've got.) "Don't ask me, I only work here."
Granted, you might also be just about to need a fan clutch in the 1992 - since they seem to last 3-4 years in the XJ (four years TOPS - I change them every three, whether it needs it or not. It usually does. Take a Sharpie pen or an engraver, and initial and date the thing when you change it. It helps you keep track, and is a good habit to get into on "maintenance" parts that need replacing at irregular intervals.)
As far as the heat outside - it's hotter than the hinges of Hell here in the Bay Area, and I usually have to go outside overdressed for a snowball fight. I'm a cold-weather critter, and it shows (I usually don't go for a shirt around the house until it gets down to about 55, and I'll dig out long pants around the house somewhere in the low 40's. Pants AND shirt somewhere in the low to mid 30's... I'm Scottish - whaddaya want? I also run a degree warmer than normal...)
5-90
