Louise and Felina are going to have opportunities for direct close-up contact on the track. Not sexual contact of course, but if they are close to each other they will no doubt try to obstruct the other's progress through an obstacle, interfere with the other's attempts to undo a bondage device and so on. Being bound, gagged, hooded or whatever won't stop them from those tactics: this is a live challenge.
But the assistants are necessary to help select and apply the bindings and other testing devices. It's a key point of the game that all devices that are removed and unlocked successfully will be replaced by new ones - and likely those new ones will be tougher. But if the contestant who should pick the device is blindfolded she won't be able to make a full assessment of where the other is right now and what restraint one should pick, and if she is gagged or hooded and her hands bound she will be unable to indicate her choice. So we have to take on the parts of the assistants/secundants, but they are mostly just proxies for what Felina and Louise would pick in a given situation.