Oh, I totally get that. But SL makes it that much easier.
> Don’t feel like you have to follow this advice.
I wasn't commanding anyone to do something. Good Grief.
That said, there's a marked difference between the kinds of assymetrical communication that you're describing and baby sign language. We've done sign with each of our three children and it's remarkable to watch them pick it up—they clearly understand that these hand gestures are words that carry specific meaning and get a lot of delight out of learning and applying them correctly and being mimicked and understood. The language center of the brain clearly develops much faster than the parts responsible for controlling the tongue, and sign gives them a great outlet for that language.
Also, you don't have to do anything complicated to give them just a little bit of sign, so unlike a lot of parenting advice it's not difficult to try out. Just say a word while making a sign (ASL if you want but we'll sometimes just make up one on the spot) and then give them the thing or do the thing. "More", "water", "milk", "diaper", "good night", "up"—just pick one and try it! Once you start and see their delight it's hard to stop.
As one of many, many parents, my observation has been that there is so much contradictory parenting advice because there is so much variation in the kids, in terms of behaviors, personalities, the order in which they bootstrap their motor vs verbal skills, body awareness, etc., etc. As a result, consuming parenting advice is like going down a checklist of things to try, and the kid won’t respond to most of it.