Sorry I'm still not 100% clear -- you've got a lot of address entries for @corp.com but they're in your personal address book (synced under the @gmail account presumably)?
The Exchange tab in the contact picker -- yes, that does filter, but on the "account under which the contact entries are synced" not on "the @corp.com part of the contract entry, no matter where and how it's stored".
In other words, the Exchange tab will show "contacts synced by Aqua Mail under your @corp.com account" and *not* "contacts in phone Contacts no matter where they came from but all having @corp.com in their actual addresses".