Clarke's preferred explanation for male-only Primaris recruitment rests on factory standardization, with female Custodians treated as a different case. Glenn proposes a different story: the newer Primaris process could work on women even if the older Space Marine process did not. In his proposed explanation, the Imperium's attachment to tradition has prevented anyone from trying. The disagreement concerns how to explain or change the fictional recruitment system, and Glenn explicitly distinguishes his proposed new-process explanation from a claim about the older process.
Notable Point · 5:40:24-5:41:17
Primaris recruitment, standardization and Imperial tradition
Competing explanations for Primaris recruitment contrast standardized production with an institution too attached to tradition to test a new possibility.