Rowers tend to have very high level of VO2 max, but they definitely not a climber types - they are freaking huge with a lot muscle mass. Combine this with extreme pain tolerance and you will have perfect “diesel” types riders. Of course it is hard to avoid genreralisation but there are some examples of ex-rowers with huge FTP (from american crit scene you have great example of Brennan Wertz (from Mike’s Bikes - guy that destroyed Nate and Jonathan during TT, he can put around 480W for an hour).
Rowing is extremely hard and demanding sport that is meant to kill you and simply if you combine huge aerobic potential, high VO2 max and muscle mass you will get great domestique rider that can put insane amounts of watts.