To add on further again, not only do they like to cast type-changing Pokemon as normal as a baseline (the most obvious exception being Oricorio, which has no baseline form), but Normal is the type they use for types that don't exist yet. Like fairy type, or the theoretical 'Sound' type. In addition, if they made Porygon electric, they'd then have to answer why following artificial Pokemon (like Castform) are not electric. Casting Porygon as normal sets the baseline as 'whatever is appropriate for the pokemon', so if they came up with a Pokemon based on a computer bug or an internet spider, they could type it poison/bug without having to use a type for electric.If Porygon and evolutions are virtual reality pokemon that can turn themselves into data, shouldn't they be like holograms, so ghost or ghost/electric type? Why are they normal type?
: )It's a shame that its dex entries imply that something went terribly wrong with Z's programming during its evolution.