I think the important point here is that earth is, at a local level, essentially a rigid body, but in the global scale, it’s far from rigid. You have a series of tectonic plates, floating around on viscous material, with the whole thing rotating away. So if you measure the rate of rotation at a particular spot, you’ll get the aggregate rate of rotation, with any local seismic activity, or oscillatory motion, superimposed on top. Moreover, the entire system is changing slowly - the axis of rotation changes over time, and the whole thing wobbles slightly as well. It’s fascinating stuff, and amazing that we now have devices of such sensitivity.
What we see in all of the graphs, in all of the papers and websites that we’ve discussed so far, is absolutely aligned with that - it all points to the same thing.