I contacted record buck farms (company from the last picture) a few months back and questioned them about their 1-2 gallon size citrus, whether they were just rooted cuttings or micrografted when very young and the graft was just buried under the roots?
They told me that they do NOT graft any of the citrus in smaller 1-2 gallon pots. Only their 5+ gallon size citrus are grafted. This means they were able to root calamondins, eureka beaars and meyer lemons, pink variegated lemons, valencia, blood, hamlin and navel oranges, murcott tangerines, key rangpur and persian limes, lakeland limequats, satsumas, meiwa and centennial kumquats, finger limes, among others (this list is just what i have personally seen lying around in small pot sizes). They must be rooting these under very precise conditions, because out of this list i have only been successful with easily rooting meyer lemons, persian limes, key limes. Although, i normally root things outdoors exposed to the elements anyway. Indoors once i did get a few satsuma cuttings to callous..
Either theyre rooting cuttings, or air layering. But i tend to think they're rooting cuttings since theyre such a large company..