Despite legal seperation standards it is perfectly common to still encounter some wake turbulence in situations that make the turbulence linger longer than normal. While the bumps may have in no way endagered the flight the pilot may have felt that he should provide an explanation to the passenegers to put them at ease. Sadly the pilot should haven't tried to explain the wake turbulence because it created THE FALSE IMPRESSION amoung non-pilots and "training pilots"
that it was somehow the pilots fault or ATC's fault.
I actually had something similar happen to me when I was on a flight that experienced some turbulence my fellow pilot on the PA tried to explain and ended up confusing the passenegers and one wrote a letter to complain. Another time unrelated I stated on the PA "we can continue holding here for another 5 minutes but then we will be low on fuel and have to divert." What I meant was in 5 minutes we would still have plently of fuel to go to our alternate airport but of course my foolish wording caused people to focus on the false idea of "LOW FUEL!"
So... what happened? NOTHING, it was no big deal and simply a misunderstanding. And yes... wake turbulence can be encountered at all altitudes and with legal seperation standards.