To prove that shoot the arrow into one of the foam block targets. Shoot it lengthwise into the target so that the arrow does not protrude out the other side. When you remove it you'll feel it rotating (in the reverse direction in had in flight) inside the target as the blades follow the same path of entry.
I have done exactly this and the arrow
does stop spinning when it enters the target, at least when I have used a muzzy phantom, slick trick, g5 striker, muzzy 3 blade and a couple others.
I have used BH's that
do continue spinning into the target:
Crimson Talon BH's would spin "through" the target. You have to twist the shaft to get the arrow to remove properly.
A single bevel BH also spins "through" the target. It rotates also when pulling it out.
IMO the loss of energy with arelatively heavy arrow is probably negligible. But I am still probably going to use a single bevel BH next year
.