The BTC balance shows the available balance only, therefore if a user's UTXOs belong to unconfirmed transactions, they will not be included in the balance here.
Note: The funds are safe, but there may be a temporary time span while the UTXO is processing that the balance will show 0. To understand why it does this, please read the example below.
Example: If Person A has a $20 bill and needs to pay Person B $5. They must hand over the entire $20 bill and wait for the change. With UTXOs, the basic principle is the same.
If you fund the BTC address with 20 BTC and want to send 5 BTC. You must send the 20 BTC and wait for the change. During this period while the UTXO is processing, the balance may reflect 0 for a short period of time until the transaction is complete and the "change" is returned.