has Apple decided they only want app store approved software on your iOS?
(a) You would have encountered this behaviour on 10.8
(b) Its not "Apple decided" ... if you read the description of the default policy in System Preferences its "Mac App Store and identified developers".
Therefore the fact that Google can't be arsed to digitally sign their installers is not Apple's problem, its Google's arrogance.
The default policy of "App Store and identified developers" is for your own good, "Anywhere" is an obvious risk, and "App Store" although safer (because of the malware screening Apple do before listing on App Store) is obviously more restrictive. So the default policy gives you the best of both worlds.