This just refers to to GM bulletin with a some added commentary. When I searched for the use of abrasive discs causing engine damage, the only thing I found was the GM bulletin and articles that referred to and just add more commentary. I could not find real world evidence of engine damage.
I’d be very curious to see a real world example of engine damage caused if someone has it. Because I can’t find it.
I’m not sure how much material you could physically remove on purpose when using a White/fine grade bristle disc on aluminum machined surfaces. It would also depend on the metallurgy of the part. However if it’s an engine part made that handles high heat, it’s likely not a soft material. The amount of abrasive dust when used properly is so minimal that I don’t know if it’s able to be feasibly measured.
Bristle Disc's themselves contain Aluminum Oxide, This is directly from the 3M website.... "For increased performance, Scotch-Brite™ Bristle Discs feature aluminum oxide blended with ceramic abrasive grain"
I don't use abrasive disc's when doing internal work on engines, transmissions, transfer cases, or differentials mostly because GM training from years ago.....I remember a lot of the "old heads" in the shop having the same stance as you. GM went to the extreme of back charging for engine replacements if abrasive disc debris was deemed the cause during an audit of the core.
Don't even allow the use of abrasive/cut off wheels in my shop if a Engine/Transmission is being built or open for repair.
While this isn't exactly an exception to the rule.....In extreme cases, I will use an abrasive disc on a removed engine component.
Let's take a Rear Main Adaptor used on one piece Gen I & II small block Chevies for example, The composite paper gasket turns to Stone after awhile.....I use Red Scotchbrite Pads to remove the gasket from the adaptor, But I do it out back behind my shop, Then blow it clean best I can, Wash it in solvent, Then blow it with clean/virgin solvent, Then blow it dry.