The short anwser is that they shouldn't count it twice. When they review the applications they should see that it is the same account and also because it is notated as an "A" in the ECOA, they should not take it into consideration to your debt to income ratio because technically you are not financially responsible for the debt.
One issue that does come up is when they have difficulty matching up the accounts an example is how AMEX uses a system that doesn't show the actual account number but instead sends a random sequence of numbers which may be different than what is showing on your husbands, since sometimes the application process is done by an automated system it will count each as a separte account and that is when you may need to advise them to manually review it. Either way an AU account usually should not be factored in but as always it may be the discretion of the lender how they handle it.
