It's always a matter of perspective. Why do they phrase it the way they do?
Probably because the total number of hours isn't overwhelmingly high. That's why they break it down to hours per player. And since this disaster is preferably played by hardcore CoD fans, this number naturally appears higher, allowing them to package it as advertising and promote it extensively.
I'm sure they would have preferred to advertise with sentences like 'the most overall playing hours within a week in the entire CoD franchise,' but that simply didn't happen.