If it helps, in my experience contorta pushes needles before just about all other pines I have, regardless of ambient conditions, and they all go at almost precisely the same time regardless of which subgroup of contorta they're part of (murrayana, latifolia, or contorta (shore) ). Are you able to group the early pushers and see if they share common attributes?
Also, pollen cones might help make the distinction as well, though banksiana and contorta are so darn close that maybe not.
Another thing:
Even within contorta, when you become a real lodgepole/shore nerd, you notice quite a bit of diversity in characteristics, so I would hunt for anything that can reliably disambiguate these two and be super careful in relying on observations like "under 2 inch needles" and attributes that can easily be wildly different due to cultivation / vigor. I have lodgepoles both with needles far longer than 2 inches and also far shorter (note: no disrespect to
@Potawatomi13 who is sharing valuable data points) . I feel like the seed cone is the way to go, but in bonsai cultivation you might not see those very often unless you get them very vigorous. Even with the seed cone though, I feel like there is sometimes more difference in seed cone apperance between subgroups of contorta than there is between contorta and banksiana, so again, be cautious!