Satoshi test is meant to provide proof that one has really Bitcoin funds in a certain wallet (Bitcoin ownership). There are some clients who are demanding proof so this is the best way to convince them of the evidence for them to appreciate and trust one another. Satoshi test can never be utilized as a way to hack into a person's wallet because had it been that way then no one will ever be using the test anymore.
only talks about some clients because majority of them would really ask a proof yet we are talking money on here.Theres no way on hacking someones wallet on that satoshi test thingy.