As it seems, the alpha version of the Google app contains some interesting information. Even though the alpha versions are not generally available to users, or at least not the Google app itself, beta versions are indeed sent to testers for installation. However, regarding the Google app, some users who were registered on the beta channel had the chance to see an alpha build.
This situation is rather unusual and nobody knows for sure if the company plans to release these builds to more users or not. The most interesting revelation in the latest APK is the fact that it hints to the Google Assistant feature becoming available for other devices except Google Pixel. This might be possible after installing the alpha release for the Google app.
Moreover, it seems that the Assistant is now working for users who already have the particular app build. Details say that it should be running on Android 7.1.1 Nougat and 6.0.1 Marshmallow. From the tested devices, the Nougat one was surely the Nexus 6P, which is either way a Google device, but the Marshmallow one is Samsung Galaxy Note 5, which proves that Google wants to rollout the feature to other devices besides Pixel and Nexus.
There is another possibility that the Google Assistant would not ask you to install Android 7.0 Nougat, but you may need to run at least the 6.0.1 Marshmallow version. Both devices that were mentioned above could use Google Assistant after pressing and holding down the home button. This process can also be used on other devices too, if Google releases a more stable version of the Google app. However, not all the devices that have the alpha build installed proved to work with Google Assistant when holding down the home button, but the perspective is thrilling.