But it does help. If you use half a can to top off, the old style will leak out by the time you use it again.
Sometimes I need a can and a 1/4 to top it off. This way you can spin the can off and it will reseal and you can use the rest later.
Why did they switch from r22 to 410 Or R12 to 134 to who knows ??? Why did they change a freaking gas can?? Ever see what one does in a car???