As with most things, with the exception of our opinions on Christmas & Easter, I’m with Cobber. Unless you have a serious sports car where the driver needs to know how everything is going on & where the slightest drift in an indicated value might spell trouble, the gauges supplied in cars such as ours are as Cobber says comparative indicators. They are indicators of things being about quite right, or Oh shit somethings adrift. If you consider the processes in your temperature indicator; current flows through the temperature sender, which is on the left hand side of the engine block right at the back & this is a thermistor, a resistor which changed value as the temperature changes. They can be positive temperature coefficient or negative, one increases in value as it warms & the other decreases. If the current then flows through a meter movement the meter will indicate that change in value as the thermistor changed in value. QED
If your temperature gauge is showing an increase in value then more current is flowing through the network. I have never come across a gauge which implies more current is flowing than there actually is. I can think of a mechanism which would allow this to occur but the chances of this are vanishingly small. The other device within the network is the sender; for this to give you an erroneous reading it would have to drop in value* passing more current than normal & thus increasing the deflection on the meter. This type of device when on the point of failure usually go high resistance, you then get a reduction in indicated temperature. A similar effect to this can occur when PTFE tape is wrapped around the sender thread to prevent leaks. This tape can prevent the system working all together. Corrosion will have the same effect.
So I’m sorry to have to piss on your chips but I think your going to have to look further & in a different area to resolve your problem.
* depends on positive or negative temp coefficient.
Have you given the coolant system a good old bit of blood letting, it might just want a good burp.
M