Most calculations of MAX-phase electronic and mechanical properties begin with an unstated assumption: the material carries no magnetic moment, so spin polarization can be switched off from the first step. Usually that assumption holds. It is not universal. A handful of MAX phases, once manganese or chromium enters the metal sublattice, develop a real, measurable magnetic moment, and once one family member is confirmed magnetic, the non-magnetic ground state of every other member stops being a safe default. This paper tests the assumption for six molybdenum- and titanium-based MAX phases studied together for the first time: Mo2AlC, Mo3AlC2, Mo4AlC3, Ti2AlC, Ti3AlC2, and Ti4AlC3. Three of these, Mo3AlC2, Mo4AlC3, and Ti4AlC3, have not previously been examined for magnetism. Using all-electron density functional theory, we compare spin-polarized and non-spin-polarized total energies, converged magnetic moments, and spin-resolved densities of states for every compound, and supplement these diagnostics with a quantitative Stoner-product estimate for every metal site. All lines of evidence agree, and none comes close to the ferromagnetic instability threshold. A parallel comparison against chromium, the M-site element closest to that threshold among early transition metals, throws the six compounds' behavior into sharp relief. We then trace the answer to how the molybdenum 4d and titanium 3d bands differ from the manganese 3d band that supports magnetism in this family. This is a short paper with a simple message: verifying non-magnetism costs little next to a full property calculation, and every other property computed for these compounds depends on this check.