A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 9 July 2008
Eastern Hub Port Equipping is a Battle/Open action for you. After the first Battle action resolves each turn that attached a card to one of your Personalities: You may take an additional Battle action.
Panda Spirit Spirit • Nonhuman This Personality cannot assign to attack the turn he attaches this card, as the tranquility of the panda settles in. Battle: This Personality gains +3F.
If I am using EHP and assign to attack, am I able to attach Panda Spirit as open action in battle since I would have already assigned?
Zen Faulkes (rules official), 9 July 2008
If I am using Eastern Hub Port and assign to attack, am I able to attach Panda Spirit as open action in battle since I would have already assigned?
Yes, for the reason you gave.