The mutability and denigration of power levels is about as common as the reduction of rape to mere shock factor. Just as the 'strongest' never really is the strongest, so likewise is 'rape' detached of its actual effectualization. These things exist for sake of existing. No heroine is ever raped, no power level is ever maintained. However, wherever an exception to the contrary is found, so likewise its other, meaning if you want concretized power-levels retaining their significance all throughout, you've got good luck getting them in WN/manga where the heroines are actually raped.

Case in point: Goblin Slayer
Platinum > all
Case in point: Mushoku Tensei
You already know how that one works.

What you're reading is half-assed when a compromise against absoluteness is made.
Rape happens. Heroines get broken. Wars lead to death. Pain is painful. Good isekai understands this well.