That's excuse-making. Come on, these producers spend a season building up to "surprises" that the Internet nails within days of their set-up.
No - they gave some blatant hints (especially in the episode the week before tonight's) that it was MU Lorca we were dealing with. They by design gave viewers who were playing close attention all the clues they needed.
I didn't buy the fan theory:
"The Lorca who Captains the U.S.S. Discovery is actually from the MU..." until last week (and even then I wondered if they were just throwing the stuff where Burnham commented on how the light of the MU seemed different; and the scene showing her being served in the MU exactly the same thing we saw Lorca eating in an early episode of ST: D. Lorca's also been shown a 'light sensitive from his first appearance.
I'll be honest and say I'm disappointing that they have Lorca being from the MU because I think he was a character more in the actual TOS mold - but that's what happens when you let the guys who worked on ST:VOY (which was crap front to back) do their interpretation of the TOS era.
Still, it's pretty obvious it wasn't a secret they were desperately trying to hide/keep from the audience (and if they had I sure many would have considered it a cheap last minute stunt - but it's clear this was another planned story element/twist from the very start - and they were dropping hints to the audience all through the season (IE Lorca's oddly shaped scarson his back; and the fact he slept with a Phaser in his bed and his reaction to the Starfleet Admiral waking him in an earlier episode).
Again, it's not a deal breaker for me, but I do find it disappointing that he's not from the version of the Star Trek Prime Universe they are presenting (which I'm also sure that while it's very close to the PU the actual TOS TV series and films we've seen for the past 50+ years, it's also now obvious these writers intention is that it's still not the actual TOS PU that the original series and films took place in - and that's fine with me too at this point).
ETA:
My score:
8
Again, somewhat disappointed the these writers made the Captain of Discovery Lorca a 'transfer' from the MU; but as I said above, it's also obvious the PU that Burnham and the U.S.S. Discovery of this show came from ISN'T the original Star Trek series PU (just something somewhat close in a lot of ways) too.
Kinda wish the actual writers WERE actual fans of the TOS era. But after this, no they don't come across as such for me. Not a deal breaker though as their 23rd century universe has some interesting aspects, but their ST:VOY roots are plain to see.