I think my thing about tagging descriptively is that I don't usually have two (or more) characters just sitting or standing still while talking, and I want to keep the reader aware of what they're doing in the midst of that conversation.
And that action can do a lot for the story. Consider two people in a kitchen, talking. they could just sit at the table, or they could be cooking together. or cleaning. or putting away groceries, whatever fits the story, right? and then *how* they do it will add another level. Are they a well coordinated duo, or is there a fight for control of the task, or is one person trying to do something and the other one is ... standing around, not being helpful (and adding fuel to the conflict by their inaction?) or is the other one "helping" but just getting in the way? Lots of possibilities, for me, so I try to incorporate this kind of action into the dialogue.
Does it come out muddy or obfuscated? I hope not.