Correct, but not just suburbia.
There is great variation in how urban areas are covered; some - such as Manchester - have individual neighbourhoods/districts with articles whereas others - such as Birmingham - are structured by the wards of the city council with redirects to these from the neighbourhoods' names.
Do we know how/if the data cleaning took into account stub articles and redirects?
They are better covered with respect to current population, but not
with respect to Land area..
I suspect that a couple of phenomena are at play here. One is that
many of our articles are about historic sites and they are more evenly
spread as many predate the great drift to the towns in the nineteenth
century. The other is that every little settlement merits an article,
whilst large slabs of Suburbia are lumped together.