I can’t vouch for the author at all, but this seems like a nice detailed, technical look at the difference between the two.
TL;DR the 212CD is very good at what in biology would be called “sit and wait predation”. It’s designed to sneak into an ocean floor crevice and hang out there, possibly for for weeks until something comes by, and then attack it. The Hanwha offering, on the other hand, is less superlatively stealthy and maneuverable, but is much more flexible, allowing missile launches and likely having a much longer range.
No guarentees in life, but it is a bold statement with no evidence that comes to mind. Can anyone name a single nuclear armed country who was invaded?
All wars since nukes have been proxy wars by great powers. Russia is exceptional, in that it invaded a weaker, non-nuke non-threat country and flubbed it so badly guerilla strikes are hapening behind its front lines and frankly, across the country. They weren’t invaded, and Ukraine poses no real threat to the USSR so there are still no examples to support your statement.