FED evidently disagrees, at least in some situations:
"When A1 goes out of bounds voluntarily or by accident, or delays his return after being blocked out by an opponent, he commits an illegal participation foul when he returns inbounds. The spot of the foul is where he returns inbounds."
CB 9.6.1 SIT A (Comment)
Actually NFHS does not disagree at all.
9-6-1 deals with A & K only regarding leaving the field and returning.
Accidentally or intentionally does not matter, all that matters is did he leave with an exception if he was blocked out.
9-6-2 deals with all players
intentionally leaving the field only and doing anything to influence the play which may or may not involve returning.
These should not be hard concepts to grasp. The only difficulty for 9-6-2 should be gauging the player's "intent".