Beardie Acting Strange

So I purchased two mountain horn dragons at the weekend, one, I think the female, decided it would be a good time to explore outside the vivarium. She had a run about and climbed up the blinds to a spot perfect for my beardie to see her.
Once he caught a glimpse he started acting strange, doing the arm waving and bobbing his head 3 times. When he didn't get a response he turned around to face the wall and started digging. He's done the digging a few times and I wasn't sure why but I think it's because of the new mountain dragons I purchased.
When I let him out to play on the floor, he peeks into their vivarium. I don't want to stress the MHD's with a giant beastie, since I only purchased them a few days ago. But I also don't want to upset my beardie. He's been dark coloured since yesterday when he's usually bright yellow
Any ideas what I can do, is there any harm in letting them see each other and is it a good idea at all?
Lastly, I thought the arm waving and head bobbing was a communication tool between beardies, showing that they recognise them or as a submission :/
Can they communicate with other lizards?

It was probably an attempt at communication. I'm not sure if it's understood by other species but I wouldn't be surprised if the gestures are understood to an extent. The change and new roommates may have him a bit stressed out so I'd keep them apart as much as you can and block his view of them.