I see this mentioned a lot but there is no feature request for it yet. The answer is always “it’s supposed to do that” which I get, but I think there is a case for it to not do that. I would be willing to bet the case for it being the way it is is the exception rather than the rule. Most people will want the default invoice terms on the invoice, not the default estimate terms. This has lead to delays in payments for me more than once as customers do not get the relevant payment info sent with an invoice.
I am sending an invoice, the default option should be to send the default invoice terms. At least make it a configurable option so I don’t keep sending out invoices with no payment information on them.