There are three reasons for Google not to report results of a control-case test:
1) It didn't occur to them to run a control in their experiment.
2) It did occur to them but they decided not to do it for some reason.
3) They did run the control but it did not bolster their case.
As you point out, if they ran it and it bolstered their case there would be no reason not to report it. Of the above reasons, #2 seems the least likely (because it's easy to set up a control and it would better clarify the situation). I do not have enough evidence to judge whether #1 or #3 is more likely.
1) It didn't occur to them to run a control in their experiment.
2) It did occur to them but they decided not to do it for some reason.
3) They did run the control but it did not bolster their case.
As you point out, if they ran it and it bolstered their case there would be no reason not to report it. Of the above reasons, #2 seems the least likely (because it's easy to set up a control and it would better clarify the situation). I do not have enough evidence to judge whether #1 or #3 is more likely.