Canon basically is hindering buyers of those cameras to reuse old generic flashes, buy the very cheap and simple ones, or buy non-Canon used ones. At least as long as adapters are not available. Current and new Canon compatible models will be updated.
It could impact also some people attending photo courses - i.e. studio ones - where what is made available to students are often simple radio controls not specific to any camera. If Canon was aiming these camera models also to schools, etc. the removal of the central pin looks an ill-advised decision.
The linked article thinks the 600EX is the only flash available from Canon, though - it's not good reporting.