I've been having the LTE dropping issue extensively since day one with my Pixel XL. Happens when fast moving (car), slow moving (run), and still at my house. I can consistently get it to happen just walking from the front of my house to my back alley (seems to switch towers). Switching to 3G COMPLETELY alleviates the problem. Not a single drop anywhere.
Spoke with Google, who was useless (told me to get a new SIM, check some settings, talk to Sprint.) I did these, emailed them back, and they told me to talk to Sprint again.
Sprint has tried, but been less than helpful thus far. Spoke with tech support who had me try to reprovision a number of times (they kept giving me HTC dialer codes which didn't work, which baffled them). They put in a request to check the towers near my home, but this isn't something that only happens there. I did notice (by driving around with Signalcheck open) a nice long stretch the other day where I had multiple tower changes and no drop at all. I've been meaning to look at the tower maps to see if perhaps there's some correlation.
I had this type of problem way back when LTE was just rolling out with my Nexus 5 too. I've got drops with my XL in a number of the same places, though, never had the problem in the slightest with my Nexus 5X.