Having a few of those phishing test emails actually get snagged by the spam filters wouldn't actually a bad idea. I can review the quarantined and spam email for the rare case there is a false positives, and it's entirely possible that someone could find something in there, be like "hey that looks legit", and get phished.

Though on the subject of spam filters, I really wish IT would invest some resources into some better filtering. I mean, it's the first line of defense and from what I can tell they just use some default crappy Microsoft filter that barely catches anything and lets some of the spammiest spam just sail right through. So I guess in that sense not letting the fake phishing emails get snagged by the filters is entirely believable.