That test would be nearly worthless for all but a handful of items.
Maybe on a dated item like a contract, or perhaps a multi signed item with signatures that rule out any date but pre 35 for all the signatures. but not on some memorabilia.
With the new pigment.
Pre 35 item dated - ok, but only exclusionary.
pre 35 item undated - means nothing. For example a 33 Goudey signed in 1940 could have the new pigment. On something like a team ball, if one signature had it but others didn't that would be suspect, but not certain proof that one signature is fake.
Without the new pigment
Pre 35 dated - looks good, but a faker at the time like a clubhouse guy or wife would have used old ink too.
Post 35 item - means less the closer the assumed date is to 35. Old ink stocks, inks that don't use that colorant etc.
As an ink pigment, there were plenty of inks that didn't use it even into the 1960's. (as determined by the Postal inspection service who presumably knew what they were doing. )
https://scholarlycommons.law.northwe...2&context=jclc
since pthalo blue is mostly lightfast, it's very likely that blue inks without it are still used today.
should autograph experts add some science to their "toolbox"? Probably. Is that science expensive? sort of, I looked at machines for non destructive spectroscopy, and it seemed like a minimum of $30K and I couldn't find one with a generalized database - databases specific to metals or other narrow fields yes, generalized ones no. Not a deal breaker, but that would force a user to interpret the raw data themselves, and not everyone knows the chemistry well enough.