I've got to admit it does fit perfectly in the existing lore, I just wonder why it wasn't explicitly stated from the get go.
Runesmithing's your classical magical cyborging, then there's some really high power Clerical that can regrow limbs (personally think Clerical healing shouldn't be able to do that), Alchemy (The Potion of Regeneration Kardel invented) also regrows them in a far more in-depth and fulfilling way, and I wouldn't be surprised if the Druids have done a couple of tree arms and an alterationist/enchanter has attempted it at least once.
In light of that, another way of using magic to replace limbs is just another piece of hay in a haystack and in of itself pretty harmless and the only reason I can think of of why you'd be asked to do a separate "addition" lorepost would be that it wasn't explicitly stated in the first place. In terms of lore there's no problem here I can see.
To those worried about the runesmiths:
While there are no shortage of prostheses they all do their own thing. Runesmithed ones, for example are big, bulky and look like golems or robots: they're clearly unwieldy, heavy, agonising to attach and uncomfortable but do the job. They're not suited to fine work in the slightest but they do have a crude sense of touch as far as I know. These ones are lighter but fragile, delicate, completely numb, and look like a porcelain doll. Still unsuited to fine work because it's stated to have no sense of touch (you do have a sense of position provided it's the same size as the original, that's not lore, that's biology). Compared to the dwarven ones they're still unsuited for fine work but they're also easily broken: they win out only in aesthetic and maybe a little in weight, even though they're actually more tiring (pretty sure dwarf ones are thanhium powered).
Plus, as Arcane Puppetry derives some magical principles from Soul Puppetry (don't ask me how, I don't see the connection between porcelain avatars and voodoo dolls) technically dark magic and vunerable to clerical, no?
In short, based on the lore and what Hex has said, the dwarves still have the edge here, they're not exactly going to be replaced by a storm of puppet limbs.
So lorewise we're solid. I'm a little worried about the attitude but that's got nothing to do with the lore itself.