This may just be a tooltip issue--I'm not sure. I'm going solely based off of my experience.

I was playing a bot game today, and I noticed that when I successfully Culling Bladed a target, in addition to a 40% move speed buff, it also granted a 40 Attack Speed buff of the same duration. However, when you hover over the skill, it says "When an enemy hero is killed with culling blade, its cooldown is reset, and Axe and nearby allied units gain bonus movement speed" (emphasis added).

If this is not intentional, I believe that it may be part of what's contributing to his popularity. If it is intentional, Icefrog pls nerf BibleThump (did I do twitch chat right?)