You did that wrong - ur supposed to open rad valve before you dose and attach the can - the bullet in the can prevents the system pressure forcing water out the tube - attach the can and its dosed in a few secs. Remove can from tube . Shutand the bullet acts as a NR valve. Shut rad valves and reattach bleed screw - or the whole nipple as u removed. Way you did it with valves closed meant you put a lot of pressure into a small space rather than spreading it through the system which is why you got a problem trying to remove tube. Do that in a smaller rad and it won't all go in or might even blow the tube out.

You didnt say turn the radiator off

Nice vid …It’s never nice adding inhibitors to those rads 🤦🏼‍♂️ gimme a towel rad any day haha. 🎉