Threats of the Round:
protgren destroys this core and works very well in realistic scenarios. You can't switch gren into any attacks but the whole point of gren is to bring it in on doubles, get spikes or shoot off dangerous coverage moves that turn into stabs.
Counterplay to this one is very limited. Sure, rockium does a ton, but clef can play mindgames even then. The reason it's granted threat of the round is that it's not only super threatening to this core, but to nearly all team-structures that feature chomp+ferro.
the clanger does it again. There's not much to say here, it's not even meant to destroy this core as it is the rocks-setter but it does so many things and aside from garchomp critting earthquakes, K-O gets rocks up AND obliberates this core.
Also not much to add, it wins against this core. It's not seen often within the meta, but it is threatening to some builds and most of all does fit on stall teams, as you mentioned. Realistic scenarios are the one thing im worried about but it should still be enough to be threat of the round.
Additional Notes:
While Latias is threatening to the core, if an unboosted, nonstab hp fire is the best thing to hit ferro with then it's gonna sit in your face anyway, especially if it gets a leech off. Furthermore the set is not very strong and every decent team has a good switchin. Furthermore Chomp+Ferro especially is oftenly paired with mons that take advantage of it. Example: Tapu Fini
While it is a very nice submission, ferro does set up hazards in it's face and physdef tangrowth only fits on very specific builds. It does very well against chomp/ferro in a 1v2 situation if healthy but I feel like it's too restricting and specific for a threat of the round. Thanks though, it's important to have it listed here.
This Mawile has trouble coming in on either of them, it doesn't like hazards and the strat doesn't work if it gets leeched. The set overall is a specific cteam-build that isn't very consistent, as it loses to pokemon mawile should normally beat. In specific situations it does work, not only against this core, but it's a bit shaky. Does deserve it's mention though.
on the other hand..
Short Notes on other Submissions:
BIG NAUGHT
obliberates this core. Is unviable. absolutely obliberates it and gets 3 layers of spikes as well. Still unviable.
I love it but it's just unviable im sorry LOL