It could be. Even if that setting is mainly there to prevent too long times when using flash in dark environments. Here the problem is the flash doesn't want to use short times. But I haven't tried if the 1/60-1/250 limit actually caps the top speed too, in spite of having high speed flash enabled.
I'm of the opinion that instead of using this limitation to which exposure times can be used in Av mode with flash, it's better to use M mode. Hence my inexperience with this setting.