The spring seat is what is commonly blamed for front end clunk. Your strut mounts should be good, but can be evaluated by the shop that is installing the struts. The strut mounts are much more expensive than the spring seats, so you don't want to replace them unless they really are bad.

And yes, people do not always get the terminology correct. The spring seat holds the top of the spring in the strut. The strut mount is what holds the top of the strut in the car.

A not listed possibility would be the sway bar bushings, but I assume that your mechanic checked those while replacing all of the other suspension parts.

Phantom