[grandchild]

I think it's not answered in the slides. Instead they offer two hypotheses for the _characteristic_ of the observation of the declining length-of-day in the last 20 years, with all known effects removed such as the Metonic Cycle: Random walk & Linear.

They present the consequences of adopting one or the other prediction model, but only because one has to be adopted for practical decisions. Not because we necessarily know what's going on.

We can't know now which is the correct model. As always, only time and observation will tell.