I've always played it that a non-Verditius cannot use a lab text of a Verditius. Arm5, page 102 first column "The Lab Total is calculated in exactly the same way when working from a Laboratory Text as when working without one." I take this to mean that a non-Verditius cannot reproduce what the Verditius did so therefore cannot use the Lab Text.
Also, allowing this use devalues the Mystery of Verditius. Other breakthroughs cannot, generally, be used by non Initiates. Why should Verditius Mysteries be used?
my two cents,
Rich