It varies between airline to airline. If the Kingair is opeated on a multi crew AOC then it is recognised as multi crew time. Some airlines will recognise this (ie: Easyjet who require 500 hours of multi crew experience for the).
However British Airways request 1000 hours on turboprops over 10 tonnes for direct entry FOs on to the Short haul fleet, therefore the Kingair time would not be count towards this requirement. So I think this is where you may have derived this rumour from.
To be honoust if you get offered a job on a King Air operated multi crew then take it if you have no other options, multi crew time in a King Air is far more valuable than VFR instruction. The majority of operators will view multi crew time even if it is multi crew ops in a single pilot aircraft as good exeprience.
Also remember some operators as an insurance requirement will carry a safety pilot on a King Air; in this instance the aircraft is still operated as a single crew aircraft and the second pilot / safety pilot is not able to log the time (the safety pilot does not need to be rated either). Though that said most operators still consider safaty pilot experience as a plus point on the CV.