728 Part Marking on ATTiny414

I had a customer send an a email letting us know about the parts that he bought.
He wanted to share this information with us.

The Attiny414 I purchased from DigiKey have the following markings on them.

Atmel 728B TK

These units do not have temperature sensor calibration data loaded onto them and therefore the internal temperature sensor is not useful.

I was told by Microchip support that the 728 marking means they are engineering samples and do not have calibration data loaded.