What John said
Generally if this was not in the scope of the new permit, you don't see it. Just like the lack of AFCIs or other things we can allow on the grandfather cause
If you did want a totally compliant new generator installation (all other things being OK;
You could choose to install a sub with transfer equipment for the emergency generator circuits (without the dryer)
You could use non-SDS transfer equipment where the neutral is not switched and the main bonding jumper stays in the current service disconnect.
You could extend the dryer SEU to a breaker in your new "main" panel. where the service disconnect and main bonding jumper resides.
There may be other solutions too but chances are nobody would ever care if you just left it alone. I do tend to agree that this has always been a potentially dangerous exception, even though we did not really pile up bodies and NFPA did well to get rid of it.