Maybe it's not that the founders don't understand convertible notes. Maybe they are taking the funding at a lower valuation because they're willing to gamble on the likelihood of a (big money, not acqui-hire) acquisition by Google later down the road is more likely.
Google Ventures, in my experience, tells entrepreneurs that they have little to do with Google. They do not invest in things because they are synergistic with Google, and they may even invest in things that compete with Google. They make it very clear up front that Google Ventures is a separate organization. At most, they may tap into their network within Google to assist you if it makes sense, but any investor worth their weight in Silicon Valley can connect you with Googlers and other important companies.
