IANAL, but I think what they are trying to say here is "We are not a bank. Dear SEC, please don't treat us like one - go ask Metropolitan for all your regulatory cravings".
"Therefore, each Customer is a customer of the Bank", ehm, does the bank know about it? Each bank account must have a legal owner (or multiple ones for a joint account) and I somehow doubt Voyager would put their entire customer base as the joint owners of their bank account.
The "Cash in the Account is insured up to $250,000 per depositor" part is deliberately misleading. As far as the bank is concerned, there is only one depositor - Voyager.
In general, you need to look at specific scenarios:
1. Voyager goes belly up and you still had $1000 on your account. You could:
1.1. Sue Voyager. The court will likely rule you as a creditor granting you a claim against some fraction of their residual assets. You will get anywhere between $0 and $1000 depending on other creditors, their claims and the amount of remaining assets. Quite likely, not much.
1.2. Sue the bank. The bank will show that the omnibus account still holds some USD (that might be less than the end users' deposits) and will tell you to go sue Voyager as a creditor.
1.3. File a claim with FDIC. They will tell you to bite dust because they cover the business between the bank and Voyager. You are neither of those and have no business with them.
2. The bank goes belly up. Voyager will file a claim with FDIC and get $250K for ALL users. This will make them default on the users' claims, hence go to 1.1.