The problem with not offering tight connections at Brussels Midi/Zuid is that the total journey time becomes much longer for UK-Netherlands/Germany, making rail much less attractive compared to the alternatives. Of course this exacerbated if denying passengers the option of a 20 minute connection means making them wait for hours, but even adding another 30 minutes makes a significant difference to a journey of around 5 hours from London to western Germany, where air and rail door-to-door journey times are similar. Often significant sums of money are spent in building new infrastructure to reduce journey times, with the stated aim of making rail more attractive compared to less environmentally friendly alternatives. By taking multiple small measures to make tight connections more attractive (e.g. booking passengers with connections at the front of the Eurostar), rail should hopefully be able to gain modal share (in some cases, such as this one) without large outlays. Of course passengers for whom time is not a priority should be able to choose a longer connection time.
When my ICE was cancelled on this route in 2012, I had my ticket stamped at the Belgian Railways' international ticket office and then travelled to Germany by Belgian IC to Liège and then on regional trains.