There doesn't seem to be much behind this. Huawei made the choice to go with Alexa over Google's assistant for it's own reasons, according to Andrew's source; "It’s likely that Huawei made the decision in order to be in Amazon’s good graces, given that Amazon is an important seller of Huawei phones to U.S. customers." The post also mentions that Google has selected a single partner for the Android One (probably LG), and the blogger speculates "You’d have to think this is going to cause even more friction with Android OEMs. The smartphone market is slowing down (in the US as much as anywhere) which could mean some wondering whether it’s worth competing if Google isn’t making the field level (as well as playing in it the game itself)."
So we have one probably unrelated decision by Huawei, and some idle speculation from some blogger. No real information to support it. And even if he's right, as others have pointed out, the OEMs are the ones causing major problems in the Android ecosystem, with their inability to provide updates, and their insistence on stuffing their phones with bloatware and crapware that does the same job as the Google defaults only worse, and completely unnecessary clunky UI overlays.
I can only applaud Google's making sure that there are at least a couple of "clean" Android handsets on the market (fair disclosure; I'm a long term Nexus and now Pixel user). I'm pretty sure Google would play ball with any OEMs that were willing to return the favour, but they mostly want to preserve their ability to crapify Android, and try to divert users away from Google's ecosystem. That's their right, but you can't expect Google to be entirely happy about that.