The first year I did ToC (2016) they still did age categories whether you were in the Race or the Sportive (this was when you could still qualify from the Sportive pens, so there wasn't a Gran Fondo pen) and they were NOT well policed. A load of people kicked off about the fact that older riders were going off with the younger ones and drafting to get a better time so the organisers made a rule change on the fly that if you went off in the wrong pen (they could tell by what time your chip crossed the start line), then while you weren't DQ'd as such, your time would no longer count as an official qualifying time. This of course led to people thinking on the day that they'd qualified only to find out they hadn't when they looked at the results online and some who went home thinking they'd missed out, to get a letter later saying they now had, due to results of others ahead of them now being thrown out.
Fast forward to 2017 (which I entered but had to withdraw from late on) and they promised that they would police the pens a lot more strictly, although from people who were there, it sounded like they didn't need to as a lot of riders had learned their lesson from the previous year and made sure they were in the right pen from the start!
By 2018 (when I had a deferred entry) they'd changed it to Race, GF and Sportive and as I was in the third category, it was just a mass start pen, so I didn't get a close up look at whether they were policing the other gates properly or not. How it is now, I don't know, but generally ToC have always seemed to learned lessons from previous year's mistakes, so I think they would probably at least try to keep a reasonable level of effort on this to avoid further complaints.