This was my interpretation:
Everyone including Al had to know Lance was doping.
Alberto is under the misconception that more is better. (Hence why he has so many gadgets. He's never satisfied). He assumed an additive effect of L. carn to whatever he/Lance is currently doing.
Kind of how some super rich people are also stingy. Yeah, they have a million dollars, and they figured out how to con the system to get another $50,000 free, and they feel smart and entitled to take it.
It's like an addiction thing.