I don't think the GPL says what you think the GPL says.
I'm thinking of a scene from The Princess Bride...
Undextrois, the GPL covers the distribution of software and modifications of that software. If i.ph modifies WordPress and distributes it without sharing or making publicaly available the source code including those modifications then they would be violating the GPL.
Building their services (I have not looked at i.ph) on top of WordPress.org's software and not attributing it to WordPress does not violate the license.
It would be nice if they added a "Built with WordPress" on their site but not doing so is still okay with the GPL.