CEW:
All you are doing is moving the weak point, and actually increasing the leverage arm to the place of fracture (now behind the foot. Footing sleeves like those used on carbons are 90% to prevent mushrooming. as a direct impact drives the internal components backward and splits the hollow shaft. By ringing the area, it can't expand. I have broken as many of my footed arrows as unfooted, just in a different place. Ironically, if the interface is square and the insert set properly, there is a lot less need (and for the record, I do foot my arrows - but for length).
It also helps to hit your target, and not the post it is attached to or the rocks behind it.....
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BobW