Company-issue manuals override the buff of the other manual?

[Millybonk]

Is it a bug or WAD that the gathering manual overrides the buff of the crafting manual, and I effectively lost the GC seals with which I bought it?

Both buffs have a unique name + their tooltip doesn't highlight a potential conflict of buffs being overridden.

[Sabora_Makingai]

They work like glorified FC buffs. You can only have 1 active at a time. I used the Gathering one to level all of my gatherers while also getting the mats needed for leveling crafters. Once they were 70 and I had my mats, I switched and am currently using the crafting manual.

[Niwashi]

Both buffs have a unique name + their tooltip doesn't highlight a potential conflict of buffs being overridden.

I think at least this part seems wrong. If only one can be active (which seems to be the case, and apparently intended), then the tooltips should tell people that.

[LalaRu]

You need look at the category of the item, only one per category can be active. Manuals are in "other". You can have one "meal" and one "other" together, as example.

Some food can stack and it is in description, dunno if there are stackable "other" manuals.