Note that the article said the animal mummies come from AFTER the time of Ramses II. It seems that the Egyptians mummified a few animals for most of their long history, but it wasn’t until the XXVI dynasty that they began doing it on a large scale, embalming enough animals that it became necessary to give them tombs and cemeteries. Aside from the Apis bulls, of course, who got their own tombs from at least the XVIII dynasty onward. By the way, last week I listened to a podcast which said that before the priests embalmed an Apis bull, they would cut off a few choice pieces, as if they believed consuming steaks from the bull would give them the strength of the gods.
Of course, giving an animal an elaborate burial was the logical conclusion to centuries of animal worship. They continued the practice into Greco-Roman times, because by then it was “the Egyptian thing to do.”
As you know, I agree that the 19th and 26th dynasties are basically identical.