If you nametag a mob, it prevents the mob from despawning, except in the case of vexes, wandering traders, and other exceptions. In the most recent snapshot, this is still the case with mobs clicked with a nametag. However, mobs spawned from a named spawn egg despawn when unrendered. I tried this on a ravager while testing the Mace, I teleported to Y-lvl 1,000, and when I fell the ravager had vanished. I was able to repeat the phenomenon with a vindicator, and other ravagers, even when floating up in creative mode as soon as the mob leaves render it despawns. So, it seems mobs spawned from named spawn eggs aren't being preserved from despawn at the moment.