No. In fact, the opposite is quite true. To be really flexible, you also need to be really strong. THnk about it, Gymnsasts are felxible, and pouind for pound are about the strongest poeple out there.
I've seen big 250+ lb bodybuilders and powerlifters drop into full=splits.
If you train for strength and you traibn for flexibility...you will be strong and felxible. If you neglect one or the other...well, you either won't be strong or you wont be flexible.
Additionally, when it comes to dynamic flexibility, then strength real;ly plays a role as the msucles needed to get ones limbs to their extreme range of motion need to be strong.
Look up programs like elastic steel or relax into stretch for a good rundown on how strength plays into flexibility.