This group has currently not been a strength of the team so far and not necessarily hurting the team either (Robinson missing those to FT vs Nets almost hurt the team). Garza has only been on the court with Robinson for <1 minute and not at all with Queta. So yes, this is center by committee.
I see Queta and Garza as being pretty much as expected. Queta is +9 per game in about 20 minutes and Robinson is -5.8 per game in about 20 minutes. Queta has been good, Robinson has not been that good, and Garza does not matter as much because he does not play as much, but has been fine.
To me, Robinson has been a disappointment so far. Less than I was expecting. It is only 4 games on a new team so he deserves a little more time before any final judgement, but so far, not so good.