Ah, I guess I misread (in my own research) or somehow missed that a degree change in Celsius was directly pegged the same degree change in Kelvin (shifted by 273.15 ) when the Kelvin scale was updated to be pegged to the Boltzmann constant. Thank you for helping me understand where my understanding was flawed!
I guess I still don’t understand the utility of Celsius, though. If it’s really just an alias, shifted by 273.15, for Kelvin, what utility does Celsius offer? Why not just use Kelvin?