I am certainly not an ExPhys however I have to agree with Carl and Doug to some extent on the following point:
Here is an extreme example but should illustrate how it is possible to win a race using strategy where you might not have won even if you ran a PB. Can't speak for rowing so much but since my background is running I'll give you this answer.You know, over the years I’ve gone round-and-round with both coaches and athletes on this very issue. And this attitude floors me every time. If you want to beat someone, will you have a better shot at doing it with your PB time, or a time that’s slower than your PB time? Think about it.
If a 200 Meter specialist were to enter an 800 Meter race (Would never happen) his best chance for winning would be if all the runners jogged the first 600M at a very easy pace and then sprinted the last 200 Meters. The 200 Meter Specialist would, assuming he is a good 200 Meter runner win every time. The 200 Meter specialist could run a much faster overall time (PB) if he ran even splits but would definitely lose the race.
Like I said this is a very extreme example but these kind of tactics happen all the time in Track Distances that are longer than 800 Meters. Each Athlete has his own strenghts. Some have a great finishing Kick while other have very good speed endurance but don't have much of a kick. The athlete with a strong kick hopes the early pace is conservative and the athlete with poor finishing speed wants to take the pace out hard to take the sting out of the kicker's legs.
Just my 2 cents worth.
Rich