>Now thinking about that and creating these nucs within the same bee yard as the hive why don’t the bees that go along with the brood that you pull from the hive just go back to the original hive when they come back from the field?<
Those that forage do.
During the first 3 weeks of a worker bee's life she's a "house" bee, staying in the hive. Roughly, the first week is spent as a nurse bee. That's when her hypopharyngeal glands are developed allowing her to produce that all important royal jelly and feed the queen and larva. The second week is when she's capable of producing wax and building comb. The third week is when the poison glands develop and her main duty is being a guard bee. Basically, during her first three weeks of life, she'll stay with the brood and won't fly away. After that first three weeks, her wing muscles are developed enough, she gets her pilots license and assumes her next role as a foraging bee, flying out of the hive and returning to her original hive location with her load of nectar, pollen, water, or propolis.
That being said, when we try to rear queens, it's really important to transfer frames with very young bees to our nucs with the capacity to feed and fill the queen cells with royal jelly.
In setting up nucs in the same bee yard as the donor hive, since these 0-3 week old bees don't really fly off to forage, these non-flying bees stay where you put the frames or where you shake them (in the nuc.) The older, foraging bees, will fly out to forage and return to the original location of the donor hive, (unless this nuc is moved a couple of miles so they can't "find" the original donor hive location.)
We can use this behavior of foragers returning to the location of the donor hive to our advantage if we move the donor hive from the original hive stand and place the nuc on the original hive stand. It really boosts the population of bees in that nuc as those foragers return to that original donor hive location. Can also be used for other methods of strengthening weak hives, splits, divides, and making increase because foragers returning to the original location (whether it's their original hive or not) with a load of nectar or pollen are usually welcomed without fighting.
Sorry if it's a bit long winded, but hope this helps. Winter bee biology is a little different, best left for another thread.