I presume this bug would affect all apps that need RWD and provide ‘sign in with twitter’. Most wouldn’t realize the error, or probably end up prompting users for DM access every time this bug occurs 
But I’m also interested in seeing how you guys end up fixing this bug. Since the current sign in window explicitly mentions that "Direct Message’ permission would not be granted, my suggestion would be to specify somewhere informing the user that this holds true only if DM access is not already granted.