It's not that Google allowed someone to potentially see the connection to Google, but that Google ensured that they (Google) would be associated with the project by informing the media. The story doesn't say "omg through investigative reporting we found that Google paid for the creation of a bitcoin client" (remember, the 20% time is not "whatever you want", but projects approved by management).
Ah, after chasing down the original announcement, I see that it does contain the phrase “Google is pleased to announce the release of BitCoinJ, ...”. Still, that is a message from the original author of the software; it is neither a press release nor written by a different party at Google, which I would expect to see if Google was actually promoting or considering using Bitcoin or BitCoinJ.
Though not yet an "official" project, Google has released a Bitcoin client. As you may remember, there were concerns here about what the government/legal reaction to Bitcoin [1] will be, and the significance of certain groups lending their support to it. EFF and SIAI accept Bitcoin donations, which helps, and this action by Google is another big step.
Previous articles: SIAI accepting Bitcoin donations, Discussion on making money with Bitcoin (Clippy warning on the latter)
[1] In short, it's an anonymous P2P crypto-currency with no transaction fees, in which new units are generated by spending computer cycles computing hashes until you find one with specific properties.