Perhaps this isn't the coup just yet. Most likely his attempts to rally the Russian military to his side failed and it's possible that he was offered some kind of deal to not be arrested/killed if he waved off now.

How he was going to hold Moscow with less than 20k troops (assuming some peeled off on the march for various duties), I didn't know. It's a huge city and 20k troops would be a small footprint once you spread them out over such a large metro area. Maybe waving off at this point was all part of the expected brinksmanship he's been playing with the head of the Russian MoD?

Interesting times in Russia!