Untapped story potential for ilClan Era, but yes I agree with you, technically Deep Perhipery is not Inner Sphere, and Scorpions are on their radar, and the Scorps are always ready for them in case they show up, thus creating the "Garrison Caste". They could launch intel per say into Periphery to see whats going on in the Sphere ?
Evolved Clan Culture reveal, more Protomech stuff perhaps ?
Exactly!!! (Maybe even protomechs that don't look like D'n'D dungeon staff and don't have whacky pilots? Man can dream...)
Keeping the taint out is important but doing it by completely ignoring events outside is foolish.
They would have to make effort to collect intel from beyond the separation line and Clan Watch should be making this their top priority.
I have no doubt that once designers do decide to bring back Star Adders and Home Clans they will write that they kept the tabs on Inner Sphere all that time by sneaking through Periphery, nabbing random people for interrogation (like Scorpions do with pirates) and listening in on all sorts comms. Perhaps even sending operatives inside for first hand accounts.
As for Star Adders, Homies and Scorpion Empire while active Watch operations have been stamped out by both sides in decades since I have no doubt that there are still agents on the ground laying low, taking notes and reporting back to the Homeworlds. Scorpions would definitely have general idea about the situation in the Homeworlds as well. Spying is still a thing and Dark Caste ships that slip out would be targeted for information gathering just as much as Inner Sphere pirates are and Homeworld and Empire's spaceships would be running into each other way out there in the deep from time to time before bailing (weaker side pulls out) and going home to report on what happened.
Knowledge of situation in the Homeworlds would be high value data that Scorpion Watch wouldn't be making public or just give away to anyone because that's not regular news, it's national security stuff. Just like Sea Foxes share the news reports from the Inner Sphere when they visit but don't disclose knowledge of events like Invasion of Republic by Wolves and Falcons or Annihilation of Nova Cats by Combine because it's military intel.
Crusade wouldn't be launched without making sure that everything is relatively stable in Coreward direction and that would require reliable information from the other side.
At the very least Star Adders plus Homies and Scorpions (their Watch units that is) are regularly and studiously watching each other's "TV stations" to stay in the loop and are going through each and every frame and sentence with fine tooth comb.
And good of you to remember Garrison Caste in the Empire, everyone keeps counting Scorpion galaxies and clusters (7 and 42) but they all ignore Garrison Caste PGCs which are hefty. It's never just touman with them anymore when it comes to home defense, it's touman + grunts and together they add up to something very sizable (it's called Imperio Militar for a reason but this is topic for different tread)