I'd add that there are usually a few stragglers waaay off the back of PBP; a much smaller %age than on TCR, and rarely finishing in such extreme multiples of the winner's time.
But the scale is very different; TCR has a much higher "scratch" rate, and riding (say) a 600k is just a tiny window on riding 4000km. So more riders will be unprepared.
Plus the route of TCR is far more attractive than PBP if you are just out for a nice (long) ride. I _personally_ would not want to spend 8 days riding the PBP route, when I could ride somewhere much nicer for a week. But crossing the alps and Yugoslavia, with just a bivvy bag? That sounds fun!
So; they're the same ... but very different!!