Usability of expandable footers on responsive websites

My coworkers and I were discussing what might be a trend in e-commerce websites: expandable footers.

Here's an example from Topshop.com:

And when expanded:

I poked around for research or studies on expandable footers and came up empty. I'm curious if there's anything out there, or if anyone has personally tested these, around usability and how usable they may be.

My first instinct is that information and links like "Contact Us" should not be hidden from users, so I'm curious about any benefits to this approach. I also wonder if this is more of a design trend to minimize the footer across the experience and not necessarily for the benefit of the user.

Thanks!