Leaking is perhaps a bit harsh, but on nearly all my tanks with jfc, there always seems to be a drop or two of liquid around the jfc-ring. But if the apropriate orings aren't tight enough, there sure is the possibility for the tank to leak like a waterfall.
My unpainted stainless steel tanks are less prone to this problem however.
But experiences from other user may vary of course.
@YouTube reviews
I've learnt the hard way, that those guys aren't to be trusted. But if you have a little bit of experience with vaping, it's mostly easy to read between the lines, and see for yourself, if the gear they advertise is your cup of tea.