Strange. The 5s is just like 5. What about variance in the testing-process? Maybe last year the 5 fel half a degree differently. Maybe the planets were more aligned or BS like this. Such tests don't prove anything unless propperly done in a series to reduce variance. And for each test they should have taken a new phone, which I highly doubt they did.
I've no details on how they tested but to me it sounds like the cheap drop-tests on youtube. Where they do different tests with the same, priorly damaged device.
To me it's only sensational crap news, all based on luck.
No surprise though, that the 5c slides better but it also might swim better, who knows.
Sounds like BS to me unless they explain how they tested.