As a regular volunteer and some-time run director at a busy event (regularly 500+ participants) we have no ability, time or inclination to get into policing the results from parkruns. We're a three-lap course and people finish after two laps every week, if we notice we mention it to them but we don't prevent them from crossing the line. If people cut corners, the only person they're cheating is themselves really, they'll have a PB that isn't genuine and is hard to beat doing it properly.
If a fast club runner picks up his 7yo daughter's barcode by mistake one morning and runs 19 minutes with it, unless he notices and emails in later, or someone else notices from the results and thinks huh I don't remember seeing a really fast young child that week, we're not going to know to go in and delete that result. Equally, if someone who on the surface looks male finishes third in 16 minutes and later it comes up that huh that person who finished third, Jay Smith in the results, has set a new female course record, I'm not likely to notice, remember who that was and think I'd better report that to parkrun HQ so they can email the participant and ask who knows what - "just checking, do you identify as female as you ticked that box when you registered?".
We're too busy getting out there hours before the event to check and set up the course, brief all the other volunteers, deal with anything from complaints about dogs or spitting, to calling ambulances for cardiac arrests or handing out plasters for trips and falls, problem solving half our equipment blowing away or everything being rained on, and then packing it all up at the end, processing the results and re-sorting 500 finish tokens back into order, then passing the kit on to the next week's volunteer. I just want to help put on the events that introduced me to running, so regulars and first timers can get outside and run jog or walk their 5k with everyone else.