>>28504936Rotom is a Pokemon, yes. This is obvious. This can't be denied. This is the ultimate truth.
However, the Rotomdex is a tool that contains a Rotom within it. It is powered by Rotom. It can't simply scan itself into the device.
Granted, it probably COULD inject its own information into it with whatever it wanted. However, in the game, we most likely won't have Rotomdex's 'Rotom Entry', and the Rotom Dex isn't going to be a Pokemon we can use for battle.
It isn't going to take up a slot.