I think its plausible, temp senders are not really that accurate in my opinion, and if you had an inaccuracy somewhere, the temp sensor would be my guess. Another possibility would be corrosion in the wire to the temp sensor (I think Chrysler or VW had a problem with this, their coolant temp sensors would leak and get into the wiring harness) anyway if that wire was corroded it would affect the signal sent to the pcm and thus the PCM would reflect an inaccurate temperature reading.