There were a few years in the aughts and early 10’s that I followed courses, optimum times, and results closely, to learn more about UL eventing.
Will make this statement: The setting of the optimum time can influence the ultimate winner in a 5*. A very tight time that few riders will make, of course adds penalty points to all of the scores that don’t make it. Depending on how the time penalties fall, enough time penalties among the top of the rankings can end up offsetting very good dressage scores.
There were periods in 4*-now-5* eventing when only five or so riders would make the time. To the point where several top riders would not be trying to make time, but rather simply be doing their best to minimize the time penalties, and rely more on dressage and clean show jumping.
On the other hand, an event where a larger percentage of the field makes the optimum time thereby elevates the influence of dressage and show jumping.
I am not talking about several riders having fewer than 4 time penalty points. Rather, even top riders accumulating time penalties that can significantly alter the rankings. Or conversely, most of the top dressage rankings make the time on xc, and then time doesn’t have much influence on the rankings.
There was controversy at one period (quite some time ago) with claims that European events were minimizing the time element, to maximize the dressage influence, thereby selling more of their not-so-fast warmbloods. Don’t know how valid that was. But there was firm belief in the theory by some influential people. Rules changes helped put cross-country optimum time more firmly back in the mix.
On the other hand, tight optimum times increase riders flying over the galloping stretches and then the big gear-down for the obstacles. Only to power back up again between obstacles. If the rider wants the best possible placing at the end.
It’s all about the math. And the discretion of whoever sets the optimum time for a given event. Hope this makes sense.