Is it possible to move the Terran base on a defend order too?
Seems like it is legal!
had a response here by a user named: Jozan

If you look at The Mobilize Order (SC rules, page 23) it does only say
transport/move units as well, but we're moving bases anyways. I think
the key points are that:

Terrans can move bases as if they were units,

and

The Defend order is treated as a Mobilize order