Google added several new features to the Pixel 4 and Pixel 4 XL with its first "feature drop" this month, but it turns out that there were even more features packed in there that Google didn't tell us about.
The Pixel 4 and 4 XL's feature drop update includes improved Face Unlock. As noted by XDA-Developers, the Pixel 4 will now use recent images of your face to continually improve its face unlock. This means that when you use Face Unlock, your phone will get an improved scan of your face rather than rely on the first image of your face that it scanned.
Also packed into the Pixel 4's update is dual-frequency GNSS support. This means better location tracking because your phone can track more than one signal from a satellite using two frequencies.
In its announcement of the Pixel 4's feature drop update, Google mentioned that the phone would be getting better location quality in Google Maps, and so it's possible that this dual-frequency GNSS support is what Google was hinting at.
Finally, the Pixel 4 and 4 XL have gained official support for eSIM on T-Mobile (via Android Police). This means that you can have one carrier on a physical SIM inside your Pixel 4 and another carrier on the eSIM and receive calls and texts on both.
Having dual SIM support could be useful in a few different situations. This allows you to try out a new network that you may be thinking about switching to full time without having to carry a second phone or ditch your current phone number. It also enables people with separate personal and work phone numbers to carry one device rather than two separate devices.
Google's Pixel 4 feature drop update is now rolling out to devices, so if your Pixel 4 or 4 XL hasn't gotten it yet, you should see it soon.