OK... yes... they call it -0.95 bar vacuum. but that's not much. (about 4~5 inHg gage?) on the pressure side... they are rated at 14 bar. (so you can see what they are really meant for)
As I said... some are OK with them... but it's not really the proper use. And, I'm sure if you take a model that is a few years old, and pull a festo apart... you will see for yourself how the hoses deform. I'm not trying to be negative or anything... but I'm just trying to get you to think about the use.
This is a debate like any other... so pick a side, and go with it.