Do not do that yet for extended partitions (containers).
This is possible, because when creating partitions, we do that on
unpartitioned space that is already "tagged" as either being "logical"
or not, and the partition style is inherited from that.
The resulting code is simpler, yet working as it should.
This will also help in the future for supporting other platforms, where
the concept of "primary", "extended" and "logical" partitions do not
exist (basically all platforms except BIOS-based PC-AT).