Time line of recent events:
8/17 - Nats place Harper and Murphy on waivers.
8/18 - Braves dumped Whitley to open a slot on 40 man roster.
8/19 - Waiver period for Harper and Murphy closed.
8/20 - Braves dumped Bell to keep that 40 man roster slot open.
8/21 - 48 hour window to trade Harper/Murphy if claimed off waivers expires.
The fact the Braves decided to keep that 40 man slot open AFTER the waiver period for Murphy expired suggests they either won the claim, or he passed through waivers and the Braves are trying to trade for him. It's possible the Braves either claimed Murphy and are trying to work out a deal by some unknown time tomorrow, or Murphy passed through waivers and the Braves are trying to trade for him right now.
How bad would Murphy be defensively at 3B? He's a below average defender at 2B, so I doubt he's average at 3B. However, claiming something as preposterous as, "Murphy would make Freeman look like Arenado at the hot corner, is laughable.
If the Braves get Murphy expect to see him get the bulk of the PAs vs RHP. Whose PAs he takes is certainly open for debate, but the Braves aren't getting him to have 5-10 PAs per week off the bench.