i definitely think an option to either copy the mod page description into the .pmp or not copy it would be the best option for everyone! i can totally see why it was implemented, both to ensure SOME kind of description is there to help users identify info about the mod if a creator didn't add any, as well as a quality of life thing so as to not have to write a description twice, but i definitely prefer to make my mod page descriptions very detailed whereas my .pmp descriptions are condensed down so as to not require so much digging to find relevant information by a user who has already downloaded it.

i figure if they need the more detailed information, i've included the link back to my helio mod page, so they can check there for further details.
personally, maybe the best option for everyone could be something like, if the .pmp already has a unique description, give the option to overwrite it with the helio mod page description or not, but if it doesn't have a unique description (i don't know if it'd be possible to check for, like, textool's default "a modpack made in textools" description or whatever it is), autofill it with the helio mod page one? that way, people who do have intentionally different .pmp descriptions could choose, but the idea of ensuring SOME kind of information is in the description in cases where no description was written to begin with could still be fulfilled? again, i'm not sure if there'd be a way to detect textool's default description (or penumbra's, assuming it has one and it isn't just blank, i've never checked), but that SEEMS like the most "this covers everyone's concerns" solution to me?