What you see in this ETS screenshot is the description text of a group object.
Select the GA (not the group object) and find the DPT it is set to in the properties pane. It is very likely set to 5.001 - maybe by some other group objects connected to it. You can select 5.010 there then.
Thank you for your answer @farmio, and thank you for all the work on the KNX binding. It is great and I enjoy using it and getting all KNX connected to HA.