I'm pretty sure there would be many follow-on colonists. The newspaper (This is the "Daily Mail" after all...) is hyping the "Robinson Caruso" aspects of this.
The main point is that one-way, they can double or even triple the amount of cargo, supplies, and "bootstrap" technology they send with them.
If the space-craft does not need to come back, they can have larger landers that serve as shelters, or once they dig underground, as "garages" etc. Or have greenhouse and "air factory" modules etc. All the return trip fuel can be extra gear and consumables. Instead of having to take the nuke-reactor home, they get to keep it for power.
The logistical benefits of one-way colonization of Mars are immense.
Taking it further, pieces of the ship could be left in Mars orbit to serve as parts of an eventual space station to serve as an infrastructure base for LMO operations. (Low Mars Orbit) If follow-on ships can dock with the station, and then ferry people/supplies down to Mars, then those ships won't even need landers, and can carry even more gear/people/supplies.
I don't have a count, but I'd say that the majority of the modern Mars mission concepts leave behind lots of gear, or have unmanned cargo/fuel vehicles for return trips etc. This is just taking it to a logical extreme to maximize those advantages.