No, it's not on purpose. For FAA purposes, you can log time THEIR way, even military time.

If you didn't do that, and have to rely on mil records then you'll come up shorter than what you were entitled to (for FAA purposes).

The problem here is that retroactively applying a conversion factor years after the fact is "estimating" and may not technically rise to the level of "logged" flight time as specified in the regs. That might get you in trouble. IMO that would be personality dependent with whoever was looking at it. If it were me (prior DPE) I'd consider it reasonable if you could aticulate your normal mission profile, flght vs. ground time.