Weight training exercises, barbell curls pointless for a trackie?

Sometimes riders will do revouts after a gym session, but that would probably be more beneficial during a plyo stage.
During a conditioning phase there's more likelihood of overreaching if riders are doing high intensity interval training after a gym session, and during a strength phase you would be jeopordising the important recovery and adaptation time by adding those on.

Not really a caveat but an addition: Optimal fat mobilising occurs at different levels of exercise intensity in different people. However, it's generally at lower intensities which is why accepted practice is low intensity/high volume exercise. Typically this exercise is a focus of an athlete's conditioning or preparation phase, by the time they get round to focusing on high intensity efforts, controlling body fat should be much less of an issue and therefore largely irrelevant to the training.

An example can be any pro sprinter: not much in the way of fat you'll agree. The strength building, speed and power training is far more effective on a fit rider, and even those national squad riders who stay in reasonable form all year round will still do a block of high volume/low intensity steady state road riding when starting a new phase after a recovery/rest period.

Obviously gym work can be used for that too (it doesn't always have to be strength work) although cycling is clearly more specific and potentially more effective. The flip side is that there is also a significant amount of strength work done on the bike, I'm always saying this, but most amateur track sprinters neglect the importance of on-bike work and are still training with the methods bandied about on forums from the Australian or East German training progs of the 80s and 90s.