Sure, but they can ask or it can be volunteered - which I was ready to do, and demonstrate if needs be because of my particular circumstances in application. IITC there also was stuff on my application which I had to put in, but which wasn't check-able by the issuer. There was also one enormous hole that they didn't ask for.
But to go back to the initial thing - that the credit assessor would view the applicant's assets and liabilities in their entirety. And the ability of an applicant to service their existing debt, and any additional being applied for
I would have thought would be a useful thing to be considered, whether or not in the mandatory govt code or simply by request to the applicant "this is optional but may assist your application if answered".