When you change the Customer:Job name on an invoice, the items on that invoice will not change or delete. Is this what you're referring to or you're talking about the pre-fill feature, which QuickBooks pre-fills the new transaction based on previous transaction? If you're referring to the latter, it only applies to vendors.
Please let us know if you have other questions.
Re: Customer Invoices
Please Learn from the input here.
For this: "it is not automatically populating the items/amts. due?"
You have to now use the Icon at the top = Add Time & Costs. Here are the Billable entries you previously assigned for that job and as billable. You have to Select if you want all of them or only some of them; that's why they don't automatically Fill the sales form. The icon is at the top of Sales Receipts, too. You control this.
Pre-fill and Recall have nothing to do with the Sales functions.