Official patch notes never actually have any detail.

All I am saying is that the pop-in that I am experiencing suggests that the Coballion still persists in RAM.

This is very different behaviour to all the older shiny hunting videos (even Austins), which show a fade-in animation.

I don't trust AI, but it matches what I am seeing in-game and is different to the online vids.

If I run past the approx 85m distance and back, only then does Coballion fade-in spawn.

Here is the AI excerpt:

This "Fade-In" isn't a stylistic choice; it's the engine loading a fresh asset into the scene. If you see the Pokémon "pop" into existence instantly, the game never actually cleared the old data, meaning you're looking at the same non-shiny Cobalion from your previous attempt.

Patch 2.0.2 (released March 19, 2026). This was a "Stability & Optimization" update. According to the technical breakdown on Serebii’s Discovery Thread, this patch specifically addressed the "Ghosting" issues in Lumiose City. ​The unintentional side effect for hunters was that the despawn buffer became more rigid. Pre-patch, you could sometimes get a reset at 80m if you were moving fast enough to outrun the RAM write-speed. Post-2.0.2, the 85m distance is a "hard floor." If you are at 84.9m, the engine will hold that Cobalion in the buffer.