Lookee what he can do! He wants a job!
I've seen some threads talking around this but after much searching I can't find an answer. We had a game this past week where a player completed the plot quest Study at the Librarium which allows the player to draw and play an extra Intrigue card when taking a play an Intrigue card action. We also had the Hall of Many Pillars building in play that allows a player to play 3 Intrigue cards. I agree with your interpretation. A more definitive way could be to see how the IOS version handles it.
The player with the Librarium card argued playing on the Hall he was entitled to play up to 6 intrigue cards (the 3 from the Hall and a corresponding 3 for having the Librarium card). My interpretation is that chosing the Hall of Many Pillars is one action therefore he was entitled to 4 total.
I've been looking for an official interpretation, or barring that, just how others read that combination. Any feedback would be awesome.