I am guessing the Russian sub was there testing Swedish defenses but was allowed to depart intact.
I don’t know anything about subs, but the pictures makes it look like the conning tower is about as wide as the sub, and the tower is about half the size of the sub.
Versatility, functionality, all started with making great pocket knives.
And whatever happened with the (many?) wrecked Soviet subs that litter the Baltic Sea Floor, some nukes, some not? The Sedes are in charge of those.
For the US to use such subs to bottle up the Chinese, we'd need sub tenders to accompany them across the Pacific, and to replenish them frequently while on station. Back during WW II the Germans used submarine sub tenders ("milch cows") to replenish their subs off the US east coast. It wouldn't be as simple as the author implies.
See today's Wall Street Journal for a big article on the new Chinese submarine fleet, and the few passages it has to get to the Pacific.
I doubt that the foreign sub experienced the “awe and mystery” of crush depth, as it would have registered on the sensitive sound equipment of other subs around the world.