Legal. The reference distance for making the call is the distance from the pin to the back edge of your marker. As long as the following foot ends up farther from the pin than that reference distance, you're still good.
Now, let's say this player pushes off with his left foot and has it in the air at the time the disc is released. The player sort of freezes that position holding the left foot in the air for say 3 seconds and then swings it forward past the marker before touching the ground. The RC is pondering whether that visible pause will be enough "proof" of balance to meet the way the rule is currently written and not be considered a foot fault.
Rater of the tossed arc.