They're still doing new builds in eastern NC. Just east of Greenville in Chocowinity there used to be no coverage but as recently as January a new site went live there. The T-Mobile coverage map still shows that there's almost no coverage there but if you drove by today you'd have full signal.
Off the bat, I think that site is meant to cover Juanita-Woodinville Way going south to site SE02523A. That's always been a weaker coverage area for T-Mobile.
That's a good add for T-Mobile, both from a coverage and a capacity standpoint.
That site is a great addition from a coverage standpoint, as it sits squarely between SE02654C and SE02628D. That being said, I was hoping they would hop on Verizon's SEA North Sammamish site (47.6019, -122.07074). I'll shoot them an email about that one.