I have noticed that if (and when) I obsolete the preset Constructor (in lieu of my own design) I tend not to get any when I chose the 3 Free as my first Pragmatic choice.  I have to remember not to obsolete that design until after I've received those 3 free ones; as the AI has no clue that SSC is short for Starbase/Shipyard Constructor.

So, perhaps there needs to be a sub-category under "Support" that lets the AI know that this is a "Constructor" or a Colonizer ("Colony Ship"), etc.

I believe I recall the same thing happening with the Colony Ship when it's been obsoleted and I choose a fully loaded free one as an ideology choice; again, the AI has no clue that NPC stands for New Planet Colonizer.

Oh well, live and learn (not to obsolete too soon in the game).