Yes and no I would say. It confirms you have a balance due from the client, so that’s something, but whether the client is able or willing to pay, is another story.

What a confirmation gives you is grounds to have the balance in the first place so there’s that. You have the right to recognize the receivable balance and it’s something you’re owed to. By all accounts your client should therefore also pay up, i.e. it’s collectable. You have an asset you have the right to in your accounts and rightfully so. 

However, whether the balance is of any value, is another matter. Value of a receivable is normally assessed based on it’s recoverability or collectability if you will. Question “will I be paid what I am owed” is asked and the answer to that gives you the indication whether the receivable is of any value.

If the answer is less than probable, you have reasons to consider this balance as “not collectable” and write it down or off the balance sheet. However, if it is more than probable, leave it as it is. If it’s something in between, maybe consider partial write-down? It is hugely dependant on the case, but to answer to the first question, I would say that “no, confirming a balance does not prove the balance is also collectable”.