But that doesnt matter too much. I find if i come up short on a gap then the wheel would get pushed forwards towards the seat tube, the chain tugs stop this from happening as they are pulling backwards on the wheel. If you dropped the bike onto the back wheel from holding it vertical, then it gets pushed towards the seat tube again, the chair tugs stop this. The chain tugs allow the chain to be set kind of tight, so the wheel cant fall out the bike backwards because the chain is pulling it towards the seat tube, again. The only way I can see them "failing" is if you have them completely undone, you come short on a gap, the wheel gets pushed forwards, and the chain slips off, the wheel then bounces back and out of the dropout, but still, the tyre wouldnt fit through the brakes, so it can't fall out.
So saying
is a lie.