Two or three hill giants would have been a great addition for the goblins in Act I and I would be surprised if the Absolute Army didn't contain at least a few hill and/or mountain giants. Since cloud giants were good-aligned, the presence of evil giants in the Army of the Absolute could serve as an IG explanation for the sudden appearance of cloud giant fingers.
"Two or three" and "A few" is the crux of the issue though.
The existence of giants isn't in question. But rather the abundance of them (Or rather, their fingers). Where there's dozens upon dozens of fingers lying about in random crates and being regularly stocked at vendors (In addition to elixirs that are brewed from the essence of 3 fingers)
So unless there's some missing information about how Giants routinely shed and regrow their fingers like how deer do their antlers, there can seem to be an overabundance of giant fingers on the Sword Coast.
