So much reading and, sadly, so much rubbish to filter
If you enter a practice autorotation, the blades rotate faster than the engines & the freewheels allow the engines to a "flight idle", ready to re-engage as soon as the rotor speed drops, due to collective input.
You are aware that a GTE's compressor will spin at around 35,000rpm, the free power turbine shaft will spin at around 20.000rpm and the main rotor NR will spin at around 250rpm yes
If the main rotor blades were to spin at 35,000rpm+ well, they'd end up in China, blade tip speed is obviously contolled due to mach restrictions
Surely you must have meant something else though?