“However in larger stuff (20mm and up) they are two different rounds and have different functions.”
What I said was that there is no SAA (including 20mm and 30mm)cartridge presently designated as a Drill Cartridge. (In the US)
Now, someone may call a Dummy Cartridge a Drill Cartridge, or vise-versa, but that doesn’t make it one. No more so than calling a Grenade Cartridge a Blank, or a 45 Colt a 45 Long Colt. ;)
In my day at least, the wood 3"/50 cartridges were called Drill Cartridges. Many of the 3"/50 Drill Cartridges were made from fired or reject cases and projectiles similar to the 90mm that you mentioned. With a brass case, the inert projectile was heavily crimped, while in a steel case it was spot welded.
I know that the Army thick walled cartridges are called Drill Cartridges. What are the official designations of the two 90mm Cartridges that you mentioned??
As I said, I’m certainly open to changing anything I may say.