Kapusta

Well I just outlined one issue in my first reply (see point #2, and consider the opposite situation).

Also, are you going to run a longer stem to compensate for the reduction in reach moving from the drop bar to the flat bar? If so, you are again making the bike more endo-prone. If not, you are going to have a fairly cramped cockpit that does not allow you to practice what is now widely accepted as good bike handling technique. I am not going to try to fully explain this, as you can learn this yourself with some Googling, but what is mostly comes down to is a super short reach it makes it hard (if not impossible) to achieve a good, balanced "attack" position. When you try to get low, you also end up having to get far back, which is not great for maintaining a good fore-aft balance. Yes, you don't want the reach so long that you can't move fore/aft, but making too short prevents you from getting low in an effective manor, and leaves you very cramped while trying to do so.

One other issue not related to the reach is the fact that gravel and road bikes have steeper head tube angles, which not only decreases stability at high speeds in the rough (an issue that is real, though I think it often gets a bit overblown), but also pulls the front wheel closer in, thus increasing the tendency to endo.