With all due respect, I find it much easier to believe that Google just did not do its homework or testing on bluetooth as opposed to believing that Google is more concerned about privacy than Apple and all these other companies. I do not like Apple at all, but its track record with respect to privacy is much better than Google's. I have been an Android person since the original Droid and HTC Eris, and Google has a consistent track record of releasing products (apps, etc.) that are half-baked and they work out the kinks as they go. Look at most of the products they have released, including the recent releases of Allo, Google Assistant, Home, etc. I think Google can fix the issues with Bluetooth if it cares to try to fix them. Unfortunately, Google also has a track record of ignoring issues that it does not care about fixing.
All that aside, who else should make sure Android works with the new bluetooth stack?
I have no idea if Google always uses the latest bluetooth because they care about us. They do it because they have to do it.
Google does a ton of meathead nonsense. I do not like Google as a company. I do not like any of these companies, though I may like some of their products or services. They are all the same greedy machine that only exists to siphon money from everyone, even those that can't afford it. All while they are exploiting cheap or free labor by using open-source software to make billions and not giving back.
That last part is the one thing I like about Google — they aren't like that and do give plenty back. They take a project, adopt it, adapt it and improve it. The Chromium project alone makes up for all the evils they may do when it comes to using the open source community (there are plenty).
Google will take the latest version of bluetooth, adapt it to work with Android, improve it as much as they can. Then they'll compare it to the very latest version, merge any changes, and commit it all back. Sometime their changes are undesirable (adding a google-invented codec or something like that) and folks hate on them, including me. But that doesn't diminish the fact that they follow through and give everything back.
But they're still greedy, evil monsters who make good phones sometimes and offer great services that you pay for (because you want to) with your life.