The section you cited is regarding the Elite Benefits Guarantee only.

It specifically redirects, in the section you cited, regarding the Ultimate Reservation Guarantee (for which what you booked isn't available/you're walked, as we're discussing here) to 4.3.a.iii, which makes no mention of any 24 hour requirement. The page with the various guarantees also makes no mention of a 24 hour requirement.

***The OP should have accepted the Element, and asked for the GM email of the Towneplace. Then once all set at the Element, drop the GM an email claiming the Guarantee.

If the GM refused, file a case with Marriott corporate and they will ensure it gets paid out, if you meet the terms of the guarantee, not including any 24 hour rule (they did for me).