I'm sure this is a silly question but is there any reason NOT to use an older style non-cartridge bottom bracket on a carbon frame? I recently built an 03 giant TCR using a 90s vintage Ultegra/600 cup/cone BB (in the correct size for the frame and cranks) and am just worried that it may somehow damage the BB shell by putting too much pressure on the carbon or something like that. Seems to work fine, shifts well, etc. Am I right to worry about this or should I be spending my worries on more important things?

Your bb is lined with aluminum, so the cups have no real interaction with the carbon - the lockring contacts the aluminum face of the bb shell on the left side, but so does the non-drive cup on a Shimano cartridge bb. Plus I can't see where the torque at the cup is a factor between cartridge-style and conventional style bb's. If the bb spins smoothly, I can't think of a reason why it wouldn't work.

I figured that was the case but had a moment of irrational concern and wanted to make sure. :D