No problem Stevie ..no offence taken from me ...its just a debate and my opinion based on personal experience..not on others opinions , theory or videos.. because as you rightly say..some can be very French.
Rather than me trying a plastic bag around my arm with and elastic band.. can I suggest you try getting into your boat wearing your waders (Although that is not the OP’s original question..it is more relevant to our side of the debate).
If you have ... and found you got no water in.. Can I ask if you wear any clothing under your chest waders and belt ? I normally wear a woollen jumper so could not get the tight seal a plastic bag with elastic to bare arm gives. If I pulled my belt tight to make the seal watertight ..I would have a very uncomfortable day on the water.
From my own self rescue experiences ..I ended up like the guy in your video link ..at 4.32 . with waders full of water. I was wearing a belt and the rubber waders that I have ..I realise he was not wearing a belt. He is a young thin and fit guy so got in the boat no problem. At my age and fitness ... I would be extremely foolish to believe I could get back into my boat because that video shows someone else doing so.
I should add that the video I made was in a post debating about cold water shock ..not drowning with waders on. So perhaps you have taken it slightly out of context. From what I understand Cold water shock is what kills most folks that fall off boats into UK waters .. That video is presumably made in a reasonably warm French pond ....so that effect is not shown .. perhaps that could slow the young French guy down ?
Have you considered that effect wearing your waders on a small boat at sea ? If some folk are correct and your belt seal fails if you fall out your boat ,,and they do get water in them and make you heavy to lift ..have you considered how you or a rescue party could get you out the water?
If you have ... and are happy with all your risk assessments ..then there is no reason not to wear them in your boat. They are just not for me ... simply because having tried it they fail my personal risk assessment tests.
To answer the Ops original question .. I still occasionally launch a boat wearing waders ..I would be a hypocrite to say I don’t but they are always removed as soon as Im on the boat when I do.
I prefer to use a Dry Suit to launch and recover on ..albiet the bottom half only ... on reasonable days. The tight neoprene waist band against my skin still allowed a little water in when I self rescued..but it just looked like I had wet my pants.. not enough to weigh me down