I've wondered about this, too. Maybe it's lag. I think the lead computing sight is server based, whereas the bombsight crosshair is on your front end. Ground textures would be in a different location in the server time-space Aces High universe than in your time-space Aces High universe. It may be like different people seeing carriers at different locations based on their latency to the server.
... a faster-than-light neutrino walks into a bar.
Then again, maybe there's a slight error in the sight?
Remembering back, we found some error in the LCG when we tested it together. It doesn't (or didn't, anyway) necessarily point where it "should" have to give us hits on each other in the TA. Upside down in particular. The rounds flew as they should have while firing inverted, but the LCG didn't seem to take bank angle/being inverted into consideration. I suspect if we'd have made any real effort to test it while firing vertically we'd have also seen some discrepancies.
Maybe something similar with the bomb end of things? Could it have been terrain-related (bombing up or down slope, maybe)?
In the end, it sounds like the LCG did its job by teaching the OP to bomb better on his own than with the LCG! Nothing says "don't get too hooked on the tool" like discovering that it isn't a perfect tool!