They did some frame interpolation on They Shall Not Grow Old to bring the framerate up to 24 fps, as silent films were filmed at rates ranging down as low as 12-16 fps and 24fps only became the standard once sound came in [it was, quite literally, the slowest film could run through the camera...
It's very weird and has that odd effect of smoothing textures and making people look much younger than they are. Very clearly DNR being used and then a VERY fine patina of digital grain being added back in. There is some very clearly colourised footage [the concert footage in Part 1], but...