No, servers are lower speed because they have more cores and larger caches. Both of those take up more die space, which makes routing higher-speed clocks harder/impossible.
This is easy to prove. The highest clock rate xeons you'll find are a special SKU exclusive to aws. Sure enough, they have far fewer cores than instances with lower clocks.
The cores have independent clock trees and PLLs. Half the point of going multi core instead of giant single core in the first place is so that you don't have to route clock lines all over the place.
What you're seeing isn't routing issues, but the fact that their newer process isn't up to snuff, and they don't have the proper yields on larger die sizes.
Like, I've shipped RTL and know pretty well how this stuff works.
This is easy to prove. The highest clock rate xeons you'll find are a special SKU exclusive to aws. Sure enough, they have far fewer cores than instances with lower clocks.