Nope. These are all myths. I do not believe in such things.
You always get best results, when you pour in the right and recommended engine oil grade, but at the same time, you must know all the previous maintenance history, engine oil change intervals, grade / viscosity poured, etc.
If not available, its best to play safe and minimise the risk.
If you switch to 0w-20 now, then your vehicle being 7 years old and driven ~160,000 Kms on Odo, there are chances that engine oil consumption may start, along with smoke from the exhaust.
Would you like it? I hope not.
That's why I mentioned to start from 5w-30 min., and take as less risk as possible.
If it suits, good, if not, then switch to 10w-30, and lastly 10w-40.