Is there a reason why the card wasn't updated in the Brood War expansion so as to be able to be used against Dark Templers and Medics? Irradiate also seems to have a similar issue. I mainly want to know if, officially, these cards were never meant to be updated.

If you want an official answer, ask your question here: www.fantasyflightgames.com/edge_faq.asp

I wonder why it works that too.

Corey Konieczka answered this question on Board Game Geek (here is the link ):

"There are a handful of unit types unaffected by Spawn Broodling that would be affected in the video game. There are no typos however, and the printed card is how I intended (due to balanced issues ect)."