I have never seen bikes tightened up from the other side and I have crossed some rough stretches of water in my time - over many years, we were even turned away from Larne port on one occasion because the ships Captain considered it too rough to take bikes

we travelled the next day instead
Obviously, it is important to not ratchet down too tight as it would be likely to damage the mountings and/or the side stand itself

I leave my bike in gear and with a broad velcro strap around the grip and front brake lever