Thats strange, I've seen a couple of gauge panels that do that as part of the POST, none that I've ever owned and I don't remember what cars they were but I've never seen that on a jeep. I also know that on some models you can do the key trick, thinking about it there is a gauge test I remember reading about in either my 97TJ or 98XJ FSM, I think it's the 98 as it does not do the error code readout. I've always had a OBDII scanner so I've never tried it. Now you have me curious.
Yup, 98XJ FSM, section 8E-11 Instrument panel systems, actuator test, depress trip odometer button, turn to ON position but don't start, release button. There is a chart on the next page, seems it moves the gauges and instrument lights in 2 second increments. Spedometer from 0-120 then 120-0, gas from E-F then F-E.