They actually didn't say no SP "content" locked behind MP, from what I remember, they said that SP game endings and what not would not ever be affected by or be required for an ending or state after ME3. If you think they said otherwise, come up with some citations.
Yes, they did :
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Mark Darrah @BioMarkDarrah 1m
And no, singleplayer content is NOT locked behind MP.
John Epler @eplerjc
To clarify, playing MP vs. not playing MP will have no impact on your SP experience.
Ability Drain @AbilityDrain
Since the characters work for our Inquisitor, will some of the items we unlock in multiplayer become available in story mode?
Mike Laidlaw @Mike_Laidlaw
No, they're separate modes.
@AarynFlynn @dragonage count for SP so my question is, IS the MP going to have ANY effect on the SP at all?
Aaryn Flynn @AarynFlynn
@user @dragonage No gated content. But we do have some cool ideas for the future, even as we keep the experiences distinct.
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It's not just the ending, it's no CONTENT. FUll stop.