el,
You are not using the MEL to work the aircraft. You are deferring a problem in accordance with the MEL. If you are pulling a C.B. for the RAT heater, you are carrying out a maintenance action to deactivate a system. The reason you are deferring fixing an item can be for many reasons and the most common are time and spares availability.
As has been discussed before, the aircraft appears not to have been in the air mode on the ground, but has had a relay with contacts in the incorrect sense . Relays fail in many ways, so the TOWS may have been working, but just the RAT probe heater contacts of R2-5 failed. This appears to be a reoccurring problem, so maybe it should have been found on previous TOWS tests, but it was not.