A Sarbat Khalsa is not, by itself, a resolution; it is the assembly that can pass one. What makes a decision reached there binding on the wider community is the gurmata, a resolution taken specifically in the presence of the Guru Granth Sahib at the Akal Takht, understood as carrying the sanction of the scripture itself rather than resting on the authority of whoever proposed it. The 1748 reorganization into misls was adopted this way, which is part of why it held: Nawab Kapur Singh could propose consolidation, but it became binding on all sixty-five previously independent bands only once it passed as a gurmata before the assembled Khalsa.
This is also why the 1748 gathering belongs on the same page as gatherings from very different centuries carrying the same name. The institution the Sarbat Khalsa names, a general assembly whose gurmata binds the whole community, is older and more durable than any single occasion it produces; the eighteenth century misl system was one strong exercise of that institution at the height of its authority, called when the Khalsa most needed a coordinated answer to Mughal pressure and delivered one that held for decades.