Wit,
You may be correct that it was a ground radar test. On the other hand, your statement that there was a line of commercial traffic at the end of the taxiway makes me wonder if wake turbulence didn't have something to do with it.
At my airport, if there was a line of commercial jets waiting to at the departure runway, you might well be better served by getting in that line, than going to an intersection, where you'll get at 3 minute delay after each jet departure. And I'm going to keep rolling jets from the end that don't have/need a delay. Far from getting you out quicker, going to an intersection might get you out much later!