The end of each stroke isn’t incredibly important, but we don’t want to chop off the end of each stroke to up our stroke rate either. You should not feel like you’re doing a tricep extension at the end of each stroke. For this drill however you WILL feel like you’re doing a tricep extension at the end of each stroke as this drill is an over-correction for finishing the stroke. Try to splash water behind you at the end of each stroke. Your hand will exit the water with more momentum than usual and you can redirect that momentum into your recovery. Do not leave your hand back there behind you for any extra time. Go ahead and start recovering the hand quickly.