I wouldn’t view them as something you do to increase your lockout necessarily, but rather something that helps build mass that will ultimately support the ability to pull heavier weights.
Additionally, properly performed they should help to increase shoulder flexibility and teach you to lock the weight out further down your thighs which is an important thing to work on.
They are going to feel awkward at first but that probably becomes more of a reason to do them.
The traditional Jackal’s Gym template has you pulling 6 singles from the floor one week and pulling from the rack the next. They utilize 4 rack heights starting just above the knee and working to just above the floor, one rack height a week, then you start at the top again and work down.
I do this cycle once a year and it is always amazing to me how sore I get and I am always able to identify a rack height that clearly needs work so I pull from that height as an accesory movement when I structure a meet cycle.
It is tough to beat heavy rack work for back mass and if you have ever seen Brad Gillingham in person you recognize he is one of the thickest lifters on the planet (he is as thick front to back as I am side to side). Rack work is a huge staple of their training. I don’t even think they know what a pull thru is.