Andrew is stating that the angle of attack at which this occurs is
the same regardless of airspeed. I believe he is incorrect in this

Andrew is 100% correct on this.

my aircraft will stall at a much lower angle of attack at 50 mph
than at 60 mph, and I've never been brave enough

That sentence doesn't make any sense at all. You may be confusing
pitch angle with angle of attack.

The only means you have of determining your AOA is your airspeed
indicator. At 50 mph, you are at a higher AOA than at 60 mph.

You will reach the same angle of attack at a steeper pitch angle at
higher airspeeds.

Same AOA = Same airspeed.