If you read the CPSC staffers article, they poo-poo XRF technology as well.
The goal of eliminating all lead based paint from commercial and residential structures is, in my opinion, non-achievable.
The question remains as to the presence of lead-based paint products in or on these structures. Structures build prior to 1978 (and in some cases up to 1984 when lead was removed from commercal paint) likely have lead paint at some level. Whether it poses a health risk without lead paint dust, flakes, or peeling paint remains open.
When inspecting a residential structure built prior to 1978, I tell mycliets that lead-based paint was likely used, and exists at some level.
Our county health department makes lead swab test kits available to consumers at low cost. Absent of taking a sample and sending it to a lab, what’s a person to do on a RE transaction. Here in NY, one has 10 days to complete a lead investigation.
BTW… lead is still used in some industrial paint applications