Isn't this a predominantly bouldering shoe? Sounds like the strip is solving a problem which doesn't exist; its pretty rare to use your heels as a skyhook surely in contrast to the general need for friction. What on earth were they thinking?
Quite the opposite. Especially on limestone and granite there are many many heel hooks where a "lip" on the heel will catch on some part of the rock and provide a better heel hook. Hence the phenomenon of people buying 5:10 Velcros and Moccs purely for a single heel hook on their project.
I kinda hoped the booster heel would be like that but it’s not. But it’s certainly grippier than the blue streak on the New VS slipper...