Cross swarms by v2 feature is not implemented yet in any client I know, yes, the latest versions of BiglyBT support Swarm Merging by v2 hash, but Swarm Discoveries is other thing.
As far as I know biglybt Swarm Discoveries work by matching size of files, but even in this case it takes a lot of time (millions of torrents) to crawl DHT network.
To implement something like this clients would announce file hash list DHT, which would come up as a big load on network itself. Better option would be giving this load to trackers, but there's no standard for this yet, announcing something like: info_hash -> [file_hash1, file_hash2...]
would need another connection method, could be a http POST request.
Biggest question here is the trackers willing to take this load.
P.S.
Did you name your torrent "testing cross swarms"? :D