As far as I understand it, the mobile part of the app - Lightroom Mobile - only works when you have Lightroom on your computer.
It then allows you to sort and do some simple edits which will transfer back to Lightroom Desktop.
SO if you want to use Lightroom desktop only, you can purchase the perpetual license for a one time fee.
If you want to use Lightroom Desktop and Lightroom Mobile, you can purchase the subscription model for photographers ($10 month)which also gives you a full copy of Photoshop, some space for storage and a lot of tutorials for both applications, along with incremental updates and changes to Lightroom and Photoshop as time goes by. Adobe has already added an updated feature since they came out with LR6. And yes, only those who are on the subscription plan can use this "Dehaze" feature now. Those who bought the perpetual license will have to wait until the next version is released. The great tutorials you get with the photographers bundle, really give it added value.
Sorry that is probably not the answer you wanted to hear.