There is no standard accounting mechanism or loophole to delay these sales. The timing and execution are governed by securities laws (Rule 10b5-1 and related SEC rules), not accounting standards. Accounting comes into play after a sale occurs (e.g., recognizing gains/losses for financial reporting or tax purposes under capital gains rules), but it does not control or allow deferral of the underlying trade itself.
Plans can be structured upfront with some built-in conditions or formulas (e.g., periodic sales on set dates, or limit orders that only execute above/below certain prices, or “price floor” pauses if the stock drops too low). However, altering these conditions later counts as a modification/termination.