This is actually an engine limitation. It's to keep the turbine blades from melting. Unfortunately, you can't measure the turbine inlet temperature very well, b

This is actually an engine limitation. It's to keep the turbine blades from melting. Unfortunately, you can't measure the turbine inlet temperature very well, because of the whole melting thing. So they determine what the limit should be, and then back calculate it to somewhere they actually can measure it (which is the front of the compressor). So, you could exceed the CIT limit, but you would run the chance of damaging the engines. The MiG-25 has famously destroyed it's engines by running to fast.