Not necessarily - although some of the more recalcitrant ones are given too much leeway [ IMO ] on a raceday, they should be sent back to the trials until they get the idea - or find a new job. But compared with overseas, the number of attendants is well below what is needed I think.
The U.S model has horses 'ponied' to the start and handed to attendants, you hardly ever see a problem [ well I haven't ], it seems to be very workable and keeps horses calm and not charging down to the gates out of control as well.
Elsewhere, most every horse has an attendant, and in many areas, are kept close up behind the gates with a tape, not buggering around 200 yards or more away. Wouldn't keep in a determined escapee, but, again, I've never noticed a problem - unlike here.