Delidding is not required. People just create theories. Of course it helps in temps but who said that every CPU has to run at 5GHz+ and high voltages ?
Sorry but 30°C difference is a BS. It's either cooling issue or faulty CPU. Generally it tops at 15-20°C under full load what in general gives 0-100MHz higher OC. If someone can make more then simply has weak cooler. I've passed it on couple of chips and also believe me, EarthDog knows what he says as he is deep in this topic for longer too.
No it's not BS. Go check overclockers.net thread about it, several hundred pages. Tons of people experienced 20-30C load temp drops and ALL hit 5+ GHz post delid. Most maxed out at 4.8-4.9 before and couldn't do shit because of spiking temps.
You know 5 GHz is a magic number for many OC'ers and it's not possible on many CPU's without delid (or serious cooling overkill). Linus hit 90C+ on all cores with two diff AIO's, 240mm AND 360mm, with a 8700K....
Some even run at 5.2-5.4 GHz post delid.. Yeah 24/7 use.. Try that on stock TIM, hahah
I have delidded like 20+ CPU's over the last few years. Easy mode. Huge decrease in temps on all of them and 200-400 MHz gained + lower temps (which means lower noise on cpu cooler and all fans in general)
5 GHz is possible on CHEAP AIR COOLING after delid. Try that with stock TIM. You'll see 100C in no time and throttling.
My own 6700K couldn't do more than 4.7 before delid.... Came from 2600K at 5 GHz, back when Intel didn't have crap TIM, no way I'd accept 4.7.