When we learn to fly we do it by numbers. Climb-out speed, cruise speed, approach speed etc. We even use that dreaded term 'stalling speed'.
But what we are really doing is setting an Angle of Attack for the wing. And while under certain steady-state conditions A of A can often be related directly to a speed, it is far from always so, and a pilot should always think A of A rather than speed.
A of A is the only thing the wing ever thinks about.
The best way to gain an appreciation of A of A is to do an aerobatics course. You will soon experience zero airspeed with no stall, and stalls occuring at very high indicated airspeeds. But the stall will always take place at a particular A of A for any given wing - it never varies (unless the wing varies - like extending the flaps).
That's what he meant, and he was dead right.
SSD