Link to US 18-disc Blu-ray only.
I don’t think there is a US 18-disc blu-ray set. That link seems to go to a third-party seller that’s importing the UK set.
It looks like if you want a blu-ray only set, you have to get the UK one. But it’s apparently region-free so it shouldn’t be a problem.
My Apologies, I see what you mean now. Good catch.