Let's break this down- 20w50- fine choice. No problem there.
Shell- quality oil maker. My brand of choice too.
SH rated- usually SH rated oil is fine for motorcycles. The major concern with car oils are with this rated SJ or higher which are "energy conserving." These are more likely to have friction modifiers (including molybdenum) which can cause slipping in a wet clutch.
Now, this is not to say all SH rated car oils are OK for motorcycles. That would take a higher level about specific oils than I have. Here's the issue: Even at SH stages, phosphorus and zinc were being reduced for emissions standards. Both of these are positive additives for older engines like ours, but it is more confusing that that. My understanding that the zinc and phosphorus standards (possibly others) do not apply to 20w50 oils the same as "thinner" oils, so they may not have reduced levels.
Again, I just don't know about individual oils. Also, while many or most SH oils, especially 20w50, may not have the "friction modifiers" that can cause clutch slippage, they also may have such modifiers....and add this complication- even with those modifiers, it may not cause a problem. The last issue is that car oil is not usually designed to handle the shear forces present with the meshing of gears in a transmission. This causes the oil to break down faster. probably not an issue if you change oil every 2000 miles, but just know oil sufficient for 3000 or 5000 mile oil changes in cars should not be used that way in motorcycles.
With all this uncertainty, for me, I use motorcycle or oil intended for diesel engines. I use Shell Rotella T. I know it has adequate zinc and phosphorus, shear stability and does not have the friction modifiers that can cause problems.
In the end, the oil you have chosen is probably fine....but as you can probably tell, oil is such a complex subject that opinions often rule over facts because the facts are so difficult to discern.