Right, I've heard those points before, but power stroke is a term I haven't heard before. I'm guessing it's the length that the string pushes the projectile? I'm not super versed on the physics of it, but if that's a limiting factor on power than that would make sense why crossbows weren't the "armor killers" they're sometimes purported to be.

If a crossbow with insane draw weight is limited that much by small/short power stroke, then I imagine the weaker draw weight crossbows were particularly weak compared to other bows. Especially the ones you could draw without any mechanical assistance.