Came across this on the water heater and furnace flues on a new build today. The first time I’ve seen them done like this. Very secure, completely encircles the vent and holds it off of the wood support.
The Super showed up with the clients during the walkthrough. I complemented him on this and asked if they were doing all of them that way now. He said he’d never seen it before. Oh well… guess it was an accident.