Ideally on a tri bike you need that drop to maximize the aero position, but this is compensated for by effectively rotating your whole cycling posture, forwards, towards the handlebars. This is the reason why tri bikes have steeper seat tube angles. So let's say I have a rider that usually rides a road bike with a 74 degree seat tube angle and we put her on a Cervelo with a 78 deg angle, We've effectively rotated her forward by 4 deg and she should be able to tolerate a lower handle bar position but it also means that her saddle has to be tilted forward by 4 deg to compensate for that. I'm simplifying this greatly, but you get the idea.

There are definite changes in body stress with this posture, more weight on the arms and shoulders, more extreme angle at the neck, knee is usually forward of the pedal axle which is harder on the knee cap although it is a more powerful position. So a full aero posture is not one that can be adopted overnight and does take some strengthening to get used to it. And some people will simply never be comfortable in this type of position. But it does not mean that a person has to have saddle pain, that's different.

The other thing about tri bike is that you are supposed to be pedaling hard enough that it takes some of the weight off the saddle. Most of us mortals can't do that for very long so I think that is a poor answer to how to address saddle pain on a tri bike.

On a road bike, lessening the saddle to bar drop does help with some of these problems.