I can confirm this. I'm running a 3700x with the stock cooler and It's idling at 50-60 degree at 3.6 Ghz. If I enable Game boost mode in the motherboard (it basically push the frequency to 4.2 and turn up all fans) it increase the performance of the CPU in cinebench from 4662 to 5087 points. That's said, the CPU reaches a whopping 100 degree!!! Probably need to get better cooler before enabling that again.

I see this as a good thing, the chip is tuned well enough to hit its limits out of the box, without having to mess around with manual overclocking to get optimal performance.

Yeah, and this is advertised in the 700X moniker. If you want an overclockable chip you need something from the *600 series.

This might be slightly wrong: I think the X is the key indicator, not the 600/700 distinction.