Depends upon model.
Ravens for example have no backup to the hangbolt, whilst all the Mainair types do. I don't think that the Pegasus aircraft range have a backup.
In practice, it's probably not the most critical "Jesus" bolt anyhow, that is the much smaller bolts in the bottom corners of the A-frame.
Doesn't stop me checking the hangbolt bloody carefully every time I rig, and given it costs about £10 or so, changing it at half the recommended interval
G