Law 19 doesn't specifically deal with bringing your own jumper safely, only when they must bring their jumper to the ground. That's why we are now getting guys posting what they have done/seen done and how it was justified.
I agree that the thrust of 19.10(g) is to not allow a player to be 'held in the air ' ( under protection from being tackled) for a protracted period of time, whilst opposition all await either the ball release or his eventual landing. This is a technical lineout offence and hense why its only a FK. It could even be considered as trying to encourage ( contrive? Draw?) The opposition into offending in some way.
10.4(j) is a law to ensure player safety, and I see no logical reason why it doesn't equally cover teammates as well as opposition, in the same way that if a player stamped on or punched a teammate then he should be sanctioned also.
In essence, all 'danger/player safety' laws apply to ALL players, irrespective of shirt colour.
In my matches, if the catcher is lifted and held whilst still retaining the ball the I shout "play it "(
not "use it" - which infers 5s to do so) ..... If they don't react to my management guidance and then its a FK , and I'd add that rarely is anyone surprised by the FK.