The issue we have is there is a base and a base theme. The current convention across markup and CSS is to use the theme name without 'theme' (e.g., 'base-') which would mean a conflict between both the base and base theme if they both use 'base'. Rather than put 'theme' in front of everything, I used the markup convention for non-theme stuff which is "wb-". It would go against the markup convention to use 'wb-base' instead of 'wb-'.

As for porting 'wb-' back to v3.0, it could be done for the base CSS if you want as it would be consistent with convention (rather than using 'base-')..