Gary, that is defintely NOT true. There are so many myths and old wive's tales about synthetic oils it makes me laugh when I hear some of the things being said. I may be stirring the pot here but another is having to wait until so many miles to let piston rings seat before changing over to syn oil. That might have been the case several decades ago but in most cases piston ring technology has advanced and materials used have changed in those several decades. Did you know that high end cars like Ferraris, Mercedes-Benz and Corvettes, to name just a few, leave the factories with synthetic oils in the engines? I always use synthetic oil on the piston skirts and the rings when assembling a new engine and I've never had ring seating problems. I use synthetic oils in every vehicle we own, the car, the F-150 and the Harleys but I also don't own anything with a flat tappet cam either, they're all roller tappets.
Mike