WhoisGuard is a service from NameCheap. Unless otherwise specified, I wouldn't assume that it would be available to domains registered through other registrars.
It also replaces the owner's name with WhoisGuard, which is IMO inferior to the way Gandi does whois privacy.
The WhoIS we are talking about in the pricing page is the Gandi one. It is not available for every TLDs has some registries don't support it. Majors one does.
It also replaces the owner's name with WhoisGuard, which is IMO inferior to the way Gandi does whois privacy.