it's weird if you haven't been on any dates for sure, but yeah depending on how many dates you're in if it's less than three i definitely think it's weird. there is nothing wrong with liking one person more than another but i wouldn't stop talking to other girls until you become exclusive with someone.
i mean even if there is a degree of familiarity, i still would prefer a discussion regarding exclusivity and labels. i also think most people go on dates with strangers/people they don't know well, hence why you are on a date with them. like i can't think of a specific instance where you would know someone well enough that you would automatically be exclusive by the first date.