> Alphabet has certainly learned a huge amount from all of these ventures, and that doesn't go away if they close them down.

This is a fantasy, and I know first hand.

I worked for a startup that was acquired by Google. They shut us down after a year. I am here to tell you that they "learned" absolutely nothing. The archived technology was never touched. Years later there were multiple teams doing stuff redundant to what we did. They didn't know we ever existed and their projects will probably never be released.