Windows Bluetooth LE connection speed

Question

We got a development chip for Bluetooth 5.0 that we want to integrate in our peripherals. For our first testing purposes we used the same chip two times which emulated a COM port. There we were able to connect the two devices and have a connection speed of 2MBit (proofed to have that by checking the values in the debugger).

So.. Now we wanted to switch to a native API via WinRT and GATT services. The laptop I use here supports bluetooth 5.1 (Dell XPS13 with an Killer AX 1650 Dual Chip for WLAN and Bluetooth 5.1) so I assume that this should do the trick.

Anyway I used the WinRT Bluetooth LE sample from https://github.com/oldnewthing/Windows-universal-samples to setup a connection and receive data but according to the device we could not manage to to setup the connection to have 2MBit but rather only 1MBit which is a bit too less for our use case.

Is there anything I can do with the WinRT API (https://learn.microsoft.com/en-us/windows/uwp/devices-sensors/gatt-client) such that I can at least check which connection speed is selected or even better can I choose a speed somewhere?

The closest thing I found was the PDU size (read only) only in the GATT Session object but no notice on the speed.

Or is there any other API I could use here beside the WinRT?