>>38831561I was uneasy at first myself, but I think we'll all warm up to it when it's revealed to just be a power created by the legendary giant for nefarious purposes or something.
The lore will save us. Like Z-Crystals turning out to be parts of Necrozma.
The lore will save us.
(Plus giant Pokémon have been in the anime since the early days)
And about them all being the same size, it seems that Dynamaxing causes a Pokémon to reach a set mass (maybe the mass of the legendary giant)
That's why Gyarados and Raichu are the same size, because they both were going for the same amount of mass, but Raichu had to grow much bigger relatively than Gyarados to reach that mass, whereas Gyarados was already big.