My guy, electricity exists because of electric fields accelerating charged elements. It's not specific phenomena.
How exactly electric attacks moving faster as time goes is unrealistic? It is expected behaviour from charged particles.
Mettaton can produce electricity from his
hands. Default assumption is that he can produce electric field, directly or indirectly
Except we already have evidence that the attacks are controlled remotely via magic and are not travelling naturally.
The argument is: Mettaton's heart produces electricity → it produces an electric field → charged particles accelerate in that field → realistic physics, real speed feat.
Even if every step of that chain were granted, it only applies to
Mettaton's attacks, because the electric field would be
his heart's field specifically. But Alphys uses the identical attack in the Asriel cutscene. Alphys has no electrical hardware. Alphys has no "heart that produces electricity." There is no electric field present. Yet the attack behaves identically.
The most parsimonious explanation that covers
both cases is magic.
Also, no, you claimed the default assumption should be that Mettaton produces an electric field because he produces electricity. But in standard methodology, the
actual default assumption is the simplest explanation consistent with
all available evidence. When the same attack is reproducible by a monster with no electrical properties, the default assumption is magic mimicking electricity aesthetically, not real electrical physics.
But the truth is, even if we consider physics here, it's still an anti-feat. Charged particles in a uniform electric field accelerate in straight lines along field lines. They don't curve, spiral, or rotate. Mettaton's attacks do exactly that. So even on its own terms, the "electric field acceleration" model doesn't describe what's actually shown on screen.