see
Pedantic Grognard
By a immediate and direct reading of the actual descriptions.Calligrapher’s Supplies 14 + 1 = 15 How is this a subset of the Forgery Kit?
Calligrapher's supplies:
"Components. Calligrapher's supplies include ink, a dozen sheets of parchment, and three quills.” -- Xanthar's Guide to Everything, p.79.
Forgery Kit:
"This small box contains a variety of papers and parchments, pens and inks, seals and sealing wax, gold and silver leaf, and other supplies necessary to create convincing forgeries of physical documents." -- PHB, p.154.
"Components. A forgery kit includes several different types of ink, a variety of parchments and papers, several quills, seals and sealing wax, gold and silver leaf, and small tools to to sculpt melted wax to mimic a seal." -- Xanthar's Guide to Everything, p.81.
So, the calligrapher's supplies has ink -- which the forger's kit has. It has parchment -- which the forger's kit has. It has three quill pens -- which the forger's kit has. And then the forger's kit has a bunch of other things. The calligrapher's supplies are, as a tool, a proper subset of the forgery kit.
Further, as a simple logical matter, if a forger couldn't duplicate everything a calligrapher can do with calligrapher's supplies, then the forger couldn't actually forge the documents made by the calligrapher. So, it's clear that a calligrapher's core skills (until we get into the "special use" zone in Xanthar's descriptions) are a subset of a forger's skills.