I spoke to Castrol about that years ago, I was getting the RS MC from Louis for DM25 for 4 ltr and wanted to use it in my E30 M3 with S14 engine. They said it was no issue whatsoever, it is not different than using a diff oil that contains a limited slip additive in a non LS diff.
They basically said do do the opposite (car oils in MC) although many people use car oils in MC seemingly without any issues.
When I think about it, what is the difference? Both have a crank, cam(s), cam chains, oil pump, rocker arms, lifters/ lash adjusters or shims.
The car engine is missing the wet clutch and in most modern bike engines the gear box.
I ran my brand new SC24 Euro spec out of Holland still in the crate (Germany still had a 100HP limit at that time thanks to the CBX), I broke it in on dino slowly (not over 4K rpm per owners manual for the first 400km) for the first 1K then switched it over to RS, it never had any other oil or any other rider.
I ran it over 240K km over 12 years and ran hard, lots of high speed Autobahn use, at 240K I did the cam chain which required splitting the cases, no bearing scoring or cylinder wall wear, all measurements were in new engine spec according to the FSM.
Imagine that on a 10w60 of all things, the transmission and long term high rpm really beat the oil up bad which is not an issue with your car, no need for an oil that heavy.
The engine had a min oil pressure of 7bar. The 4 cyl M3 never had any issues, it ran for many years on the RS without complaint, its bearing clearances were designed for heavy oil.