one thing that I haven't seen mentioned here is the angle of your saddle. the old school position always had the tip slightly up, your weight centered on the saddle so if you took your hands off the bars at any time you would still be centered. now days, riders seem to have their saddle tip pointed slightly down or level, even though this may be more aero, it increases the weight bearing on your arms. if you take your hands off the bars your weight is now shifting forward and you are not in balance.
so riding in the tri position with your saddle down and hitting a small bump is now a problem.
if you set up your bike properly and spend half of your waking hours riding it, you will be ok when you hit those small bumps, no matter where your hands are.