Bombing speeds varied based on the type of bomber, altitude of bombing, what kind of bombing mission, threat of interception, and the lead bomber's whim. Also, remember that the faster the bomber the more variables present to throw off the accuracy regardless of how good the bomb sight, navigator, or bombardier.
One thing for certain in the real deal, the odds of a B24, B17, Ju88, B26, etc, etc, dropping bombs are max throttle are slim and more so none. On the same token the only few fighters that flew around on maximum throttle were the scrambled interceptors and those engaged in combat. Also, while I dont have the information at hand I'd be willing to bet the B25's, Bostons, and other smaller and faster level bombers dropped at a higher speed than the heavy bombers due to the obvious (higher chance of interception, less variables in accuracy, etc).
For HTC to restrict one category it would be difficult to not have ramifications elsewhere. Though, I think it would be not be out of the question for bombers to have a maximum allowable speed to drop ordnance for each individual bomber. For instance, HTC cant really put a max of 240 TAS on level bombers because the B29 would need some very minute mico managing to keep it in the air that slow at high altitudes, I doubt the auto pilot could keep it level. However, the B24, B17, and Lancasters could certainly abide by that 240 TAS restriction because that was their norm. Likewise, the Mossi B Mk XVI probably dropped ordnance at a bit higher speeds than 240 TAS simply because speed was it's forte', speed was its only defense and I doubt it went in to enemy airspace strolling along like it was a walk in the park.
Ultimately the easiest thing for HTC to do would be to have a more dynamic bomb spread based on the speed of the bomber, AND have the altitude factor in as well. A B24 moving along at 200 TAS should in theory be able to get a more accurate drop than a B24 moving along at 290 TAS. If there is a slider of sorts for accuracy, I'm not currently seeing much difference between dropping at high speeds vs low speeds and high vs low altitude.
