Never heard that one and if I did I would refuse to fly the aircraft as any single engine performance will be woefull.
This rumour has been around for a while. I think enough people have mentioned it to give it some credibility - at least with particular operatores and / or LAME's.
It was given as a potential factor in the Canley Vale crash and the reason the Mojave couldn't maintain height on one engine. Of course this was never investigated by the ATSB who incorrectly applied wind vectors to radar based ground speed to conclude the pilot had inadequate airspeed control.
Setting the waste gates correctly is time consuming and should involve a flight test climb to altitude. I suspect many LAME's just skip this part and make a conservative setting or presume the last guy set them correctly.