Is it necessary?....no. Absolutely not. Will it result in poorer performance of the growing fruit?....not likely, and in many (dare i say most?) situations as long as there's bees in the patch to do the deed you will likely have a better pollination success record. Let me explain....
I have found some plants aren't receptive to pollen when we want to pollinate them....some are receptive at 7am before work...others don't want anything to do with sex in the early morning.(careful now...don't say anything she will make you will regret.......). The bees will do the deed as long as the flower is open and what they want is available which means they will pollinate the flower no matter when its receptive.But>>>>not everyone has bees anymore so if you don't have bees and you want a fruit you may need to hand pollinate.
Be aware, however, if you let the bees do the deed they can do it with pollen from you're neighbor's hubbard squash and if you grow the seeds from your fruit you may end up with something less than an AG.(but it won't make your pumpkin that the bees pollinated any less a giant pumpkin THIS year). Good luck.

I'd err on the cautious side and hand-pollenate, given that you're growing such a special plant -- leave nothing to chance.

What I did last year is to take 2-3 male flowers and use a Q-TIP to transfer pollen to the female. I then taped the female flower shut with masking tape. Will do that again this year with my AG anc CC watermelons.

Wayne