Yes, that is correct.
RAF and RN SAR crews attach a static discharger, or 'zapper snapper' to the hook. (Can't speak for the CG chaps I'm afraid.) It is designed to dangle beneath the empty hook or the winchman thereby providing a route to earth for the static. When using hi-lines, those on the ground or deck should let the hi-line earth before grabbing it if possible.
Some deck crews on RN warships still try to earth a winchman using a long probe (in the same way that cargo hooks are earthed during USLs) but this is not necessary if a zapper snapper is in use, and it certainly not welcomed by the winchman!
On most days, however, the static build-up would be unlikely to injure any one who does touch an unearthed winchman or hook, it is just a bit uncomfortable. That said, we do think carefully before winching on days that lend themslves to the build up of static, for instance in the presence of CBs.