Getting punched by someone just as powerful as you doesn't kill you. Freeza would hardly be as fearsome as he is if he couldn't take blasts as powerful as him.
But you can't block something more powerful than you with just one hand and only get a singed palm.
Heck, Vegeta took a Four-Times Kaiô-ken KameHame-Ha which he certainly had no business surviving from.
That Kamehameha had to beat back Vegeta's Gallick Gun first, and as soon as it had Goku stopped putting power into it, so by the time it hit Vegeta it wouldn't have been nearly as powerful as when it left Goku's hands.
Charging it to max would mean that, at most, the attack is as strong as he is.
Except we've seen that you can charge an attack that is more powerful than you are.
Since Goku's PL was 60 million, a charge Kamehameha will also be at 60 million.
A full power Kamehameha would be at 60 million. A charged Kamehameha would be
greater than 60 million.
That's a ki manipulation skill. Even against Nappa and Vegeta he hadn't absolutely mastered ki raising, as it took a few moments to go from 5,000 to 8,000. In other words, that 924 PL was his true maximum, not 416.
I've seen this same theory on MFG and I'll say the same thing now I said then. It's interesting but it's completely unsupported. Goku's maximum power was 416 and Piccolo's was 408. Their attacks were simply more powerful than they themselves were. Not because they were able to magically put more energy into the attack then they had but because they were creating
focused attacks with ki far more 'compacted' that normal that effectively made them more powerful without increasing the amount of ki in them. Prior to learning ki suppression there is no 'powering-up' or 'reserve power' or anything along those lines. They function
at their maximum all the time. Hence why ki suppression was developed in the first place.