This essentially negates the role of the marker if they must always be a lunge/pivot and arm+disc length away from the thrower at all times. We won’t see and hand or foot blocks and experienced throwers will be able to throw around any mark that is that far away without trouble. Let’s not even talk about the fact that such a zone would make dump and reset throws extra easy as a reset handler could intentionally use this zone for a “safe space” where their defender can’t follow them for fear of the marker touching them and resetting the stall count.
Furthermore, it has other consequences that massively favour the offence. If I cut and catch a disc and at the same time my defender makes a clean but unsuccessful bid and lands on the floor in front of me, they are technically within that zone that they are not supposed to enter in your vision of the rules.