This is a usual tactic for many online businesses to show a specially designed page for search spiders, so any major search engine has a way to verify if content is faked for them. Perhaps they use another spider that doesn't have an official UA or buy this service from a third party.

If you take a look at any website, even an unpopular one, you will see that there are hundreds of bots every day, and it's impossible to recognize what any of them is doing and why.