Paid upgrade at check-in but miles credited as original class. Normal?

At check-in I was offered a €409 upgrade from Premium Economy to Business on MUC–JFK. Seemed like a no-brainer, so I took it without hesitation.

What surprised me is that the points and status credit are still based on the original booking class, not Business. That feels pretty illogical, especially when you’re paying real money for the upgrade.

I know Lufthansa apparently mentions this somewhere on their website, but it definitely wasn’t made clear during the check-in flow. As a customer, it feels misleading at best.

Is this just how Lufthansa handles cash upgrades at check-in, or am I missing something here?