There is nothing about feed dogs on that link.

I have fmq'd both ways and I think fmqing with the feed dogs up gives me a better rhythm. Remember, your feed dogs only pull the material in one direction if you have a presser foot sitting firmly on them and your material clamped in between the pressure foot and the feed dogs . With fmq you do not have the top pressure because you are using a "darning foot" which sits above the feed dogs.

I always have my feet down. Better to be safe than sorry.

feed dogs
 

With my Sapphire 850 I like the feed dogs down. I manually dissengage ----in the past when they would creep up I could feel the quilt begin to drag. (FMQ)

When I took a fmq class, the instructor had us drop the feed dog and I've always done it that way. Now I want to experiment for myself. Thanks for the question.