The whole case for a medieval Theban script is one sentence in the Polygraphia, and that sentence has been tested. The passage Trithemius cites is not in the works of Pietro d'Abano, and the one manuscript of the Sworn Book of Honorius that carries the alphabet says it took the characters from Agrippa, who was Trithemius's own pupil, so the script travels outward from 1518 rather than into it. What that leaves is an absence: nobody has named who cut the letters, and nobody argues for a rival origin, so this is a gap in the record rather than a dispute between camps. It is one question about one script, which is why it is asked here once rather than twenty six times over the letters.
What would resolve this A witness to the letterforms from before 1518, in the Solomonic, ars notoria or alchemical manuscript traditions, or a systematic survey of those traditions returning nothing, which would be a real answer and not a failure. Failing either, work on Trithemius's own papers establishing whether he devised the script himself.
OpenHistory of Renaissance occultism; codicology of late medieval Latin magical manuscripts; history of cryptographyHonorius of Thebes; Joseph H. Peterson (ed. and trans.), The Sworn Book of Honorius (Liber Iuratus Honorii), Joseph H. Peterson's edition