Double tap to wake, that ability to wake your phone without having to press the hardware power buttons, was a popular enough feature back in the Windows 8.1 days that, after hearing some loud feedback, Microsoft decided to bring it back to "devices that support the feature."
According to a thread on Reddit, some users are getting the double tap to wake feature, although it isn't a simple process to do so. In order to get the firmware update, users first have to install the latest version of the Windows Device Recovery Tool (when we tried, our version was out of date and wouldn't update, requiring uninstalling and then installing the latest version).
If everything goes right, you should be offered a new firmware update. The original poster over at Reddit reports he installed version 16236.35018, with the last two digits possibly different depending on your region. A check of the Device Recovery Tool didn't offer that update here however, and we were unable to test it out further.
Even if you do get offered the most up to date firmware version, it's possible you won't gain the double tap to wake functionality after you've updated, as several users are reporting getting the update, but not the feature.
Microsoft should be pushing the firmware version out over the air, negating the need for using the Discovery Tool, but if you're adventurous, go ahead and try updating and let us know how it goes!