Yes, in the Half-Life engine, the Y angles are horizontal, and the X angles are vertical.
All that the plugin does is changing the way the bot moves the crosshair, that's all... it doesn't change where it wants to look (or very slightly) nor when it wants to fire or not, that is decided by the bot code, not the aiming plugin.
I have not viewed your demo yet but I'll give it a spin this evening
