With an upgraded ticket on a KLM flight you won't get the additional Miles or XP award points that a normal business class ticket would earn you.
You only get the business class seat and the associated business-class services, like the priority check-in, additional luggage (and probably lounge access where available).
- During an online check-in taking place no earlier than 30 hours before departure or at one of the kiosks at the airport, KLM can offer passengers the option of a paid upgrade from Economy Class to Business Class for part of their trip. From time to time, this option is available at a reduced rate
- After you have purchased an upgrade to Business Class for part of your trip, you have the same advantages as any other Business Class passenger for that part of your trip. For Flying Blue members, the number of Miles earned and XP gained will remain the same as stated in your original ticket. If the upgrade is paid in cash, you will earn additional Miles based on the total amount in euros you spend on the upgrade.
When you don't pay for the upgrade with award points, apparently you will get some additional award points for spending the extra cash, but that's it.