lumisphere down reliable?

[Saxi]

I ordered a L-358 and should be in today or tomorrow. I've used one twice at a local studio and very excited about getting mine. But when I used it in the studio, we kept the lumisphere up and measured each light individually, but watching the Sekonic blogs I noticed they put the sphere down and just face it to the flash to take a measurement and didn't turn off each flash individually. I asked a photographer locally about this and he mentioned it isn't reliable to do that. Is that the general agreement here? I noticed multiple video posts on Sekonic's blog use this technique, but as a major player in the light meter market, they wouldn't promote that if it was very unreliable, would they?

[PacAce]

When you have the lumishere down, the only light that gets measured is the one that's coming from directly in front of the lumisphere opening. So, if where the lumisphere opening is facing is not where the strobe is, then the reading will be much less than if it were facing the strobe. So, the accuracy of the reading would depend on how accurate the operator is in pointing the meter at the light source.

With the lumisphere up, pointing accuracy is not that important. However, if there are other light sources in the room, the reading can be exaggeated by the other lights unless measures are taken to block off those extraneous lights.