As I understand it (and please correct me), including 508 in the paperwork for a given ICT procurement is not an absolute requirement, but more of an option on the part of whoever is doing the purchasing. It should go the other way -- 508 is part of the paperwork unless the purchaser can plausibly state a reason for exemption.
Continuing on, every other 508 step should be documented as well, such as requesting a VPAT, receiving it, reviewing it, etc., all the way down to explaining the purchasing decision in 508 terms.
All of this information should be subjected to oversight, leading to improvements in 508 training and other systemic actions.
Any government-wide (or even agency-wide) initiatives on digitizing ICT procurement and management should include 508 elements as needed.