The argument for CONF 3 landings in strong crosswinds and severe turbulence is that the aircraft has more energy and is in a lower drag configuration. The increased approach speeds will also decrease the required crab angle in crosswinds. Higher airspeeds increase control effectiveness and response.
That said, the only FCOM reference I could find for CONF 3 landings is this:
LANDING
Configuration FULL, or 3, can be used.
However, Configuration 3 provides more energy and less drag.
FCOM 3.4.91
My company doesn't mention the use of CONF 3 for landing in our ops manuals but I've flown with lots of people who use it in strong crosswinds. I've used it myself a few times but to be honest, I couldn't really see any real benefit gained.