When the game suspiciously starts giving out tons of supplies be like:

yeah... and I'm Godzilla

you find it FUNNY?!?!?!?

Good question, but remember that his body is only slightly better than the average man (said exactly by the MC). They cannot force inject energy (aka Qi or Yuan Qi) into him or he will easily overload and burst, not to mention that their energies alone are way above his at the moment. So his only option is an optimal method to absorb it at his own pace - which is why MC told him not to stop until he's done, he can take it slow or fast adjustably, as long as he doesn't break.

they are doing it that way so it became is energy maybe
otherwise it would have the other energy trying to mix or cause trouble until it absorbed, so they fight to release it in the area that he can absorb

(just to be clear i dont like murim, so i dont know much about how those work, but that what seem to be the idea here)

Imagine getting gasoline for your car. Now imagine the fuel tank is gone. You'd need install a new fuel tank first.

BTW, this is not a very apt example, mind you. Since innate core energy should not be likened with dantian. But atleast you get my drift.