It can cause lot more serious problems to devs. For example if they report issues without being aware it was caused by a mod they use.Yes, using mod at this stage means you won't help the devs to find and eliminate bugs. There's no point in playing beta version with mods.
I am not sure if the devs can actually know the player is using mods. After all, the current mods are not official mods (as far as I understand it correctly) but hacks of the code itself. If this is the case the mod users could cause lot more troubles at the end.
BTW - I thought the deaf of Nozhon causing main quest issue was solved. It failed here...