Indeed. I forget where I read it, but it provides that power increase for (IIRC) some small double digits number of seconds before you need to throttle back, or the engine eats itself. If you are able to make it back to base, and that WEP wire is broken, the engine needs a rebuild before it flies again. Definitely an impressive power boost though.
The MiG-25 also have something similar where the engine redline is marked around Mach 2.8, but there's no system stopping the pilot from keeping it maxed to somewhere above Mach 3 but damaging the engine in the process.
Funnily enough I believe the SR-71 has the opposite problem, where the engines would merrily go above Mach 3.5 with no issue but the airframe and everything attached to it would get torn apart by the intense heat if the pilot tried to go any faster
No, SR-71s are still limited by engine temperature. They measure the Compressor Inlet Temperature, but I suspect that actual limitation is the turbine inlet temp. That said, it'll merrily try to go above that without issue if you don't throttle back.
Additionally, there's the Mach Cone. The shock wave off the nose forms a cone shape, with the angle determined by the speed of the aircraft. From the nose to the wingtip forms an angle of about 17.5 degrees, which corresponds well with the max speed from the CIT of Mach 3.3.
That both methods of determining max speed agree shouldn't be surprising. Skunk Works was filled with good engineers.
MiG-31 has limiter on engine controls connected to airspeed and mach number indicators, because the engine will happily run above Ma 3, with no issues.
The airframe, however, will get bent from temperature and you better hope the missile cooling loops don't fail.
The power isn't dialed down at lower speeds in order to provide thrust for maneuvering and climb.
