I posted partially about this here:
http://www.eqemulator.net/forums/showthread.php?t=29809
More so talking about the incosistancy between the graphical display of dual wield vs. the actual ability to DW.
But I think if the developers wanted to tweak the level in which the pets DW, they just syncronize those two snippets of code, and then you'll know when your pet is DWing or not just by the level check.
@what level to DW: That is a question for EQEMU, most servers may have different opinions from server to server..
Maybe make a rule_value entry for it.