You’re seeing it in black and white. Like I said, bridges require strength through a range of motion, so they are both a “stretch” and a strength exercise, depending on the variation you do and how hard it is for you. They are a great way to limber up your lumbar and stretch out your shoulders.
Generally, I would say that bridges are an excellent warm up, and what variation you use should be based on how it feels for you at the time.
Hey man don’t feel bad, stand to stand bridges are very hard. It takes a lot of strength and understanding of control. I recommend being able to hold the hardest bridge variation in Pushing The Limits for 30 seconds comfortably before attempting the stand to stand bridge. When you try the STS bridge, think of shifting your knees forward to keep your hips over your feet, and pulling your upper body up primarily through your transverse abdominis, but also all other core and abdominal muscles, plus the lats and spinal erectors. Also flex gltes, quads, and hamstrings hard to try and pull yourself forward while focusing on straightening your knees out (not bending at the hips).