When I did it last weekend for my sons car, the tabs were new in Feb of this year. They told me I would have to re-register it. I told them "the tabs are good until Feb" and they explained that is not the case any more. I had to pay for new registration and the vehicle is now registered (with new plates) until May of next year. No pro-rating happened.
As for the days to file the sellers report, you are right, there is no penalty after 5 days, but you could / would be held liable.
And of course, apologies are due. As seen in the second image, you have 15 days to file as the buyer and get it into your name.
Learned something new today.
Mostly, don't trust the lady at the licensing dept.
She obviously has not read the DOL website...
Thanks for the info:finga: