^^ Sure, that does make sense. But in a time of pretty widespread political revolution and backlash against government (which will obviously appear in every decent history book) I think that point has already been made without us being idiots. It's going to look like "this country and this country and this country were struggling to fight for freedom and finally taking a stand against their bleak political history, and at exactly the same time the best the people in the United Kingdom could do was facetiously label themselves as Jedis." It doesn't look good on our part.
If twenty years down the line other countries are flourishing and we're sinking deeper and deeper into the ground you can just see them marking little things such as this LET'S ALL TICK JEDI LOLZ way of thinking as a "they had it coming" sort of thing.
But as you say, I guess it may well be an accurate representation of UK society today, and that needs to be documented as well as any other changes. It's just a shame that we'll look like tossers.
Ultimately, as I said, history isn't really the point of conducting censuses anyway, so I guess nobody really thinks about the future in that sense.