I don't know wat you're talking about for Cap ships. I played a game recently with Vasari that they built 2 Kortuls, a Skirantra, and a Marauder before i got my ass handed to me. (Kortul is a death sentence if you don't have the upper hand from the start.)
I think the AI builds the 2 types of caps as a standard rule, and builds what it thinks it needs later. If it's building the same 2 for you, then you have become predictable and it builds more of what it thinks it needs, and believes it is working.
Just my opinion, as i don't know much about the AI's inner workings.