Books from "GuideAPI" mod are registered by the GuideAPI mod but are responsible for other mods (i.e. Blood Magic, Cyclic, etc). This means the Tome's data tag refers to any such books as having the source mod be "guideapi"

I'm pretty sure the "akashictome:definedMod" tag is just for internal use anyway as far as I can tell but for consistency I'm not sure if this is something worth looking into.

"akashictome:data": {
	guideapi: {
		id: "guideapi:mobtotems-mobtotems_guide",
		Count: 1 as byte,
		tag: {
			"akashictome:definedMod": "guideapi"
		},
		Damage: 0 as short
	},
	guideapi1: {
		id: "guideapi:cyclicmagic-guide",
		Count: 1 as byte,
		tag: {
			"akashictome:definedMod": "guideapi1"
		},
		Damage: 0 as short
	},
	guideapi2: {
		id: "guideapi:bloodmagic-guide",
		Count: 1 as byte,
		tag: {
			"akashictome:definedMod": "guideapi2"
		},
		Damage: 0 as short
	}
}

It's not a big deal to me I just noticed it and though it was worth pointing it out.