Cannot retrofit space ports to larger designs

[RemoteLeg]

I've uploaded a saved game file to your server:
RemoteLeg - 2016-07-26 - cannot retofit to larger space ports.dwg
(sic)

I can retrofit a small space port to a large space port by right-clicking directly on the port in the main window.
However, when I select the same port in the Ships and Bases screen or the Construction Yards screen it only gives me the option to retrofit to a space port of the same size.

Is this a bug? If not, surely this is a feature worth having.
Thanks.