Stretching your ligs for your penis and stretching your ligaments on your knee or shoulder is completely different. Yes ligs, like you said, don’t retract all the way after being stretched and this is very detrimental if it’s around a joint like a shoulder or knee because you need that joint to have strong short ligaments to hold it together. Otherwise it would just be dangling and the joint wouldn’t be able to move because the bones wouldn’t be in contact with each other since the ligs are stretched, but what you are completely forgetting is the fact that ligs are not the ones to make the joint move! The muscles are. So what this means is that although stretching your ligs on your knee is bad because your knee would fall apart, doing it on your dick is fine. Your dick is not a joint so all the ligs are doing is holding the dick to your body NOT MAKING IT ERECT. The hardness of your erection is not effected by your ligs because as you stated before they don’t retract/compress like muscles, that is not their job. The hardness of your dick is determined by how much blood is being held in it. The ligs job is just to hold your dick to your body. So stretching your dick ligs is fine because it doesn’t affect their ability to keep your dick to your body, but stretching your knee ligs, since it is a joint and holding two bones together, isn’t fine because then the muscles can’t make your leg move because it would just be a dangling mess since the bones aren’t being held together. Also stretching your ligs actually makes them tougher and stronger. It’s similar to strain hardening in materials. When you put something under an axial load the stress it endures stretches the material but after the load and stress are removed the material retracts a little bit from it’s stretched state, however still longer than it’s original length, and actually becomes harder and stronger. So for all the purposes of PE the results of stretching your penis ligs are perfect. But like you said before because the ligs don’t retract all the way again, stretching ligs on any joint would be extremely detrimental, but we are not doing that here are we. So stretching your dick ligs is 100% okay.