It's probably minimum phase rather than linear. I looked at the online manual and product page but didn't come across a specification. I presume it's minimum because if it were linear, they'd likely give a processing option to turn it off. The HQ (High Quality) option is there, but it's for oversampling regarding aliasing.
You could always contact support of course, if it's important to you.
I bought it when it came out and this is probably the plugin that comes across the most often in my tracks. The modular capabilities are phenomenal, I really enjoy patching stuff together to see what comes out. To see it simply as a distortion plugin is rather reductive, as it can also easily beef up drums or busses, with two envelope followers controlling the output volume, one of them being set to negative (there's a video around for that). The XLFOs also offer their share of fun, and randomization is the icing on the cake.
Some of the distortion types are a bit too cheesy, but at least we've got choice between analog simulation and pure digital bit-reduction.
Overall, I could find a use for it in almost any kind of situation, would it be to cook a bass sound, bring crunch to flat drums or even to add slight distortion in the mastering stage. WELL worth the money.