should my sour pickles be sealed while pickling?
Those pickles create their own acid. Wild bacteria that can handle the very high salt content produce lactic acid, thus preserving the pickles.

Botulism won't grow in that much salt and with how acidic the pickles are going to be when they're done. That's kind of the point of pickling in the first place.

The instructions say to leave the lid loose because the fermentation may also produce gas and it needs to escape. You don't want a half-fermented-sour-pickle bomb to go off in your kitchen.