Available Transaction Task Number on Billing Events Creation

When creating billing events, we noticed that the transaction task numbers are not restricted to only the Chargeable or Billable task numbers.

On our sample, we have removed all the Chargeable and removed 1 Billable to see if that will be reflected. However, as per checking that particular task number is still available as an option.

Is there a way to have this restricted? What is the criteria of this LOV if it is not based on the chargeable or billable options on the project plan? Also, this applies to both UI and import events creation.