I doubt that you are making any meaningful and/or important point OrbitalX - since the ways that guys use either term would depend upon the context inht which he is using such term... so at first there were guys who were seeming to proclaim that guys should not be investing into bitcoin unless they have a steady income (which they might have had referred to as a source of income or source income.. either way).
Something else to ponder here, I don’t necessarily agree with you can’t invest in bitcoin if you have no income source. When you consider your emergency funds include your dca amount as per the term; 3,6,9,12,18 etc months of funding/living. Technically you don’t have an income but you planned for the worst and can continue to DCA too with the emergency funds include kicking in, in your time of need.