SpawnActorFromClass nodes can't use the root component's default scale for the spawn transform.

On the C++ side, in PostSpawnInitialize(), FinishSpawning() is called with the scale value taken from the root component as default.

By contrast, SpawnActorFromClass nodes require a transform value, and subsequently call FInishSpawning() with that, which overwrites the default scale. Thus there is no way to "preserve" the default scale value on spawn.