Honestly man I noticed that myself in the video and there was not intent to keep it there. If anything that machine puts you in a bit of a more flat position through your legs than other variations where your legs are in more of a decline so I guess it just felt like the end of the active range for me but clearly I had more to go.
For hamstring training I do prefer to do a lying curl or any curl variation first then go into an RDL but since I injured myself RDLs are out for now which is why I basically did all curls. Trust me this is a very boring workout, honestly dont even really look forward to it, when I train hamstrings I like to do heavy RDL and a heavy press variation that is what I enjoy. Back to my selection here, I am choosing to do that particular Hammer variation first because in my opinion that is the hardest variation that I have access to in the gym. It provides the most overload through the eccentric portion of the movement which is something that most hamstring machines lack actually. For example the Hammer MTS standing curl which is the pin loaded belt driven variation basically provides no eccentric loading.
As far as the DB lying leg curl some people are very strong on this movement but in my assessment why I and most are generally weaker is because you are putting yourself through an active range of motion yet at the same time also putting yourself through a constant isometric contraction and most exercises do not / cannot provide this so its like doubling the amount of fatigue buildup while doing the movement if that makes sense. The isometric contraction which is constant is coming from having to hold the DB in place which is recruiting both hamstring as well as adductor.