The fact Jones might not ever make our team is just a testament to how good our prospect pool on defense is, not on the player. Hell someone like Braden Schneider may also have a hard time making the Rangers as a regular player with all the guys we have. Jones is a very good prospect who just had a very strong first year in college. Not every defenseman has to be tall to make it in the NHL.
One thing these players will provide is an ELC in years when we are potentially paying for our top young guys. We won't be able to keep everyone and some will not make it, but the foundation is set for when a Lindgren is ready for his 3rd contract, Zibanejad needs a new deal, and Kakko and Lafreniere are coming off their ELCs and could demand a hefty raise.
Yes, maybe someone like Jones is used as a trade chip, but that could be a very valuable piece league wide. Puck moving defenders will never go out of style. If not, he could be replacing someone 3-4 years down the line we can no longer afford or is less a part of the core of this roster.