One more vote for crab on final. Never liked the slip method in a light aircraft, and it just isn't done on a large aircraft...at least none that I have flown.
You don't tell us which they were but you might want to speculate on why the Boeing 757/67 autopilot gives a superb demonstration of a controlled slip approach (note - very little wing down with opposite rudder applied). Having been trained in the slip procedure on DC3s in winds of up to 50k early in my career I found it worked on all aeroplanes from the Tiger Moth up to said B767.
There are several drawbacks to the "Kick off Drift" school.
a) it requires a measure of fine judgement at the last minute - which has wrecked the confidence of many a budding aviator.
b) get it wrong - or forget to apply into wind aileron on a swept wing jet - and you can be left in a highly vulnerable situation as many dramatic videos testify.
c) have you ever sat in Row 40 while someone applies an agricultural amount of boot at the last minute?
The Boeing autopilot initiates its slip from about 500' and I believe has been demonstrated up to 35k or so across. The human pilot is better advised to leave the procedure to about 100' by which time the wind is more representative of that on the runway. It is vital that the into-wind aileron is maintained into the landing roll to ensure runway adhesion and lift dump deployment.
Crabbing into the flare may work for little aeroplanes in light Xwinds but have watched it go wrong too often. There is no doubt in my mind that slip in the last couple of hundred feet leads to a more consistent and polished outcome.