I'm not sure if this is related, but I am able to confirm this:
Some of the games I've installed, I've downloaded additional updates from PSN directly on the PS3, such as Metal Gear Solid - The Phantom Pain. (I know, I've been mentioning this game alot lately xD)
I had to download additional updates in order to play the FOB Missions & play Metal Gear Online. Once you've successfully got the game installed, any additional DLC or updates you download directly will work without them being resigned. (As long as they are legit, if you download them from other sources, then they will require resigning.)
I've had to do this with quite a few games.
I've noticed that alot of games that are on disc will have an update. They'll re-release the game in digital form, and won't have an update. If there is updates available on the earlier version, they usually apply those updates to the re-release so there won't be no need to update them. This isn't the case for all games, mind you. (Red Dead Redemption still requires an update either way, as the original un-updated version has game-breaking glitches on both disc & digital versions.) My point is that resigned/converted games will work with legit updates/DLC that gets downloaded to them after installation without resigning if you get them from PSN directly.