I too thought that was odd. Reverse is more effective at high speed and when landing on a runway with questionable braking action it should be your first port of call to actually start slowing down. Of course reverse thrust on contaminated surfaces can also present directional control problems.
What I though particularly alarming was that after application of manual brakes at 42knots the aircraft then "slid" for 30 seconds only reducing to 24knots before vacating the end. In my book that's practically nil braking action.
It shows that even if you've killed most of your inertia in the initial part of the landing roll it can still go horribly wrong very quickly.
A4