Deployed little more than a decade after the first nuclear explosion. Not all that advanced. And the advances actually make it easier to produce and get right. Linear/cylindrical implosion rather than spherical.
Advanced compared to the first weapons.
Thermonuclear weapons were, after all, deployed just - what - six years(?) after the first bomb.
I think that it was either a fizzle, or that it was a fake. 550 Tons is not a realistic figure for a nuclear explosion.