Did you ever get a solution to this? I'm in the same situation and confused if this is intended behavior or a misconfiguration on my part. Why would posted, unpaid invoices NOT be considered part of the customers credit?

The "posted, unpaid invoices" are in the "account balance"  which is then adjusted to credit level.   The unposted payments are not taken into accounts. 

click on the button to see the calculation.  

The "posted, unpaid invoices" are in the "account balance"  which is then adjusted to credit level.   The unposted payments are not taken into accounts. 

click on the button to see the calculation.  

Check the OST parameters in VEN and TC.  the OSTORD sets whether open orders are included in the total.

That makes sense. I've been crawling through the help files reading the various parameters associated with credit. I think we're missing configuration somewhere, because the "accounting balance" in the customer situation risk tab shows 0 (in this instance I'm looking at a customer with no open orders, but an unpaid invoice balance), while the aging balance shows what we expect.

There is an "update credit limit" checkbox in the GL account setup that is currently set to no, so I'm now trying to determine if setting that to Yes will cause the 'accounting balance' to update (after a BP balance resync?), and then properly be included in the credit limit calculation

yes - that is a new field in v12, maybe v11.  Do the customer balance resynch and that should update