I'd not heard of that...do you have a source?
If your assumption fundamentally impacts the performance of a design, then yes I think there can be harm in overestimating.
Supercruising will increase an aircraft's IR signature. But it will also extend the range of the aircraft's weapons and allow it to leave the envelope of opponent weapons faster. Given the adaptive engine designs that GE and PW are working on, it seems likely the USAF can have its cake and eat it too - it can probably have a fuel efficient engine that allows for supercruise. I don't see why you would want to delete the option, even if it might not be useful in every single tactical situation. Presumable you would delete the afterburner as well?
The ranges are still much shorter than for a radar search against a 4th generation aircraft. IRST is also somewhat weather dependent.
We will agree to disagree. Also, if not in the Pacific, then where?