#PlayStore
Looks like only a few people got this feature and it has a certain reason. This feature was not supposed to roll out to everyone instantly and it is kind of an opt-in feature without the possibility of being enabled manually.
You need to fulfil the first and only condition to trigger the opt-in notification (according to Google) - Have low storage. The opt-in notification triggers when you have left with internal storage of 2000MB (according to values in the flag database if I am understanding that thing correctly :p).
Another way to enable it - Just root your phone and use GappsMod to enable four flags.
Package - com.google.android.finsky.stable
Flags -
1. Hibernation__auto_hibernation
2. Hibernation__hibernation_installation
3. Hibernation__hibernation_my_apps
4. Hibernation__hibernation_my_apps_filter
@GappsModFlags