Marigold wasn't expecting Pintsize to do that.
This means that his personality isn't something so common that an expert would expect it, although Meena and Ellen did both talk about problematic AnthroPCs, so some degree of screwiness is typical.
Which in turns means that since his personality isn't the Windows default that it had to come from somewhere. Has he been deranged by all the porn he's downloaded for Marten, or has Marten been using him as a Mr. Hyde, an outlet for everything he's repressed in himself?
Or maybe Marigold is one of those anti-Microsoft bigots and hasn't had firsthand experience with Windows AnthroPCs.
(Yes, this is overanalysis, but hopefully it's the fun kind).