I never heard of that either,
@aart ...I turn my eggs while candling, and don't always return them to the same spot they were in the turner.
I don't think it hurts the egg if your gentle, heck, a hen turns them alot more and at different angles and not particularly gentle when they do it. Main thing is to not keep them out of the incubator too long! I candle at day 7 or 8 then at 14 and at 18 sometimes 21 but I'm candling pheasant and quail eggs not chicken. Most have incubation period of 24 days. Only have a handful of pheasants that have a 21 to 22 day period.