I'm surprised to still see that. Officially, when the 90 came out, it was an upgrade option to the 85. So, when you ordered your car, you technically were ordering an 85 with the Battery Range Upgrade option, which replaced the 85kWh battery with a 90kWh battery.
Once the 85 was no longer available, I would have assumed that they changed their model line-up to reflect that the 90 is just that, a 90. Evidently it must have been easier in the system to still leave it as an option code.