First the answer to your question...
No, being too flexible won't take away from max strength...to a certain degree that is. And being more flexible in the test you wrote about certainly wouldn't do you any damage. However, that specific test of bending over and touching your toes is not solely a hamstrings stretch. it encompasses the calves, hamstrings, glutes, erector spinae, lats & rhomboids to name the big ones.
maybe, a different approach or mind set is more appropriate. what flexibility range is optimal for you? what activity do you compete in and do you have adequate ROM for the motions you need to perform?
the other factor dealing with here is the tonus of the muscle. You can be extremely flexible and have adequate tonus which is gonna allow you to fire properly. An example of extremely strong athletes who are also extremely flexible are gymnasts and the presenters in Cirque Du Soleil.
Finally, the last issue which may need touching upon is the available range of motion. For the most part the larger you get because of increased muscle mass the less available ROM there is. Are you maximally flexible within this range and is that what you need?