It's worth mentioning that the "the other shard's time passes differently" thing is pre-existing lore from Shadowbringers, where it's specified that it's also not constant (the excuse used as to why it passed so quickly prior to our arrival, but after we showed up it started acting normal). It wasn't because we activated any sort of tether between the two, G'raha just stated it was a period of "near equivalence" iirc, of the typically fluctuating time speed.

That means that the time passing in Living Memory can be whatever the writing team wants it to be, so it's not really worth digging too much into imo.