The ceramic resonators degrade in accuracy over time (as cited in the article), which leads to non-deterministic performance of the APU, and since the entire console's timings are all linked together, this leads to non-deterministic execution of game code.
As a tool-assisted speedrun is essentially a timeline of inputs, there's no logic to account for system execution, and as such, hardware determinism is a requirement. Since an accurate emulator, barring hiccups in the underlying runtime environment, gives us a deterministic runtime environment, this works great. However, it's lead to some weird and awkward behavior when trying to console verify TAS movies on these >30 year old SNES consoles.
Replacing these ceramic resonators to repair these consoles has had mixed success, but there are folks that are successfully doing it, thus keeping these legendary consoles alive, and bringing their timings back into spec.