[jamesonquinn]

Unintentional spoilage and intentional tampering are two different things. There's nothing disingenuous about mentioning one of them but not the other.

It's true that, depending on the implementation, approval voting can be subject to tampering. But the key point there is "depending on the implementation". There are any number of anti-tampering measures that are compatible with approval. Other comments here have suggested some of them (such as using "0" vs "+" as marks). Others might rely on technological fixes (such as immediate ballot scans by multiple independent non-networked devices) or social ones (multiple witnesses during all stages of ballot collection and counting).

It may not be possible to be 100% certain of preventing every possibility of ballot-counting fraud, but it seems that >99.9% is possible, and that's basically good enough. In well-administered elections, spoilage is a much bigger problem. Thus, it's reasonable to focus on spoilage.