A while ago instead of dry hopping I started just doing a very large whirlpool hop addition.
So have you not been dry hopping your IPAs? That is a ton of hop flavor and aroma to be missing out on. To each their own, but this is akin to refusing lottery winnings because you have to pay taxes on it. Sure you do, but you'll still be rich!
But this case, you will not ruin the beer by having the fermenter open for a few seconds while you add dry hops. This is a very overblown concern, AFAIC.
If it makes you feel any better: do you know how dry hopping is done in a conical in a commercial brewery? The top of the fermenter is opened and the hops simply dumped in. Granted, their surface-area-to-volume ratios are very different, so it's not exactly apples to apples. But it does take a lot longer than 3 seconds to add 33 lbs of dry hops through a small manway vs. a few ounces.