As you can see from the attached video,the newly created partition is not shown on the device list when you try to set a mount point.
I don't think this is a wanted behavior as it is less convenient compare to the GTK Anaconda UI

Reproducible: Always

Steps to Reproduce:
1.Make some partitions
2.click into mount point assignment

Actual Results:  
the newly created partitions are not shown on the device list,you have to back to the main screen and then click Rescan to have them shown

Expected Results:  
No Rescan is needed,as no disks are added,just partitions.