As you have distinguished between "abandoned" property as defined by state law, whether you call an account "inactive" or "dormant" is a bank to bank decision. Neither term has a specific definition under federal law; there is no universal time frame where the lack of customer intitiated activity would indicate such a label is appropriate.
In my opinion, "dormant" would be more readily understood by customers and employees.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.