ALL assessment methods require evidence of accuracy and reliability. Ones currently in use have had that done and any proposed replacements or additions will also need to have their accuracy and reliability validated.
Procedures for doing this are defined in an EPA (USA) publication to allow people to use alternative methods to those officially sanctioned by the EPA for various analyses. I have gone through that process several times as new instruments or methods became available that were superior to the “sanctioned” methods. I suspect that some of that was to let practitioners do the “heavy lifting” of validating new procedures so that the EPA didn’t have to do them.