Just did a brief scan of the bill that was cited in OPs post. As far as I can tell, the scope of the bill (original and amended) is almost entirely focused on the requirements of the outgoing administration to offer transition services, and sets timelines and processes for which their services should be offered. I do not see anything in the bill requiring the incoming administration to, frankly, do anything. It appears that, while the transition services need to be offered by a particular date, there is nothing requiring the incoming administration to accept and/or use those transition services by a particular date.

The purpose of the bill appears to be to protect the incoming administration from unwanted delays caused by the outgoing administration.

The bill requires GSA and presidential transition teams to enter into a memorandum of understanding by September 1 of an election year

This statement appears to be false or misleading. Not only is there no requirement placed on the presidential candidate, no candidate would have a "presidential transition team" prior to the election. Even after being elected, that would take some time.