I think it's true. Personally I'm waiting to destroy Alduin until I've done all other missions and you can see the difference between doing the MQ or not. I applied to DLCs, it just is in my opinion, weird, after all, they may have secondary content, but the main idea is the story it has to tell.
Well, I play MQ alongside doing side missions, leaving Alduin for the last (like usual in TES games). It gets kinda anti-climatic after you finish the MQ so I also leave it for last

But I don't think the DLC will require you to kill Alduin, but just to have you know what you are. At worst, you will have to have visited the Graybeards and be proclaimed new Ysmir. At best, you will just have to unlock Dragon encounters.