By that logic services like Hoogle (a haskell search engine) are even more likely to cause confusion with other services in the same arena (search). Yet, Google hasn't barked.

I just can't see a scenario in which a person is told about Moz, seeks them out, stumbles upon Doz, and thinks they found what they were looking for. The services may be complementary and even overlap on occasion, but even to a user in a hurry it should be painfully obvious they are not the same thing.

I don't think hamming distance provides a solid legal footing for arguing conflation of trademarks. Their phonetic difference is pretty large. The legal standard is generally based on an idiot in a hurry and I think the differences are large enough than even the biggest moron with no patience will know they are different.

I don't know the statistical term for it, but the letters are on opposite sides of a QWERTY keyboard.

Which would matter if we were talking about likelihood of typos, but we're not.

Typosquatting has a larger legal footprint in copyright cases than Hamming distance, of which I can find no references. I'm not saying that typosquatting is happening here, but I would guess that typosquatting decisions would come to bear here well before HD did.