I'm more of a fan of the idea that all elements can be both astral and umbral, depending on the circumstances in which they are used.

Of course, I have no data evidence to back up this idea. All I have is the in-game lore describing the cycle of moons as being one of each element for each polarity.
ie: Astral ice = Halone the Fury & 1st moon. Umbral Ice = Memphina the Lover & 2nd Moon.
I believe it would be more intuitive if astral and umbral were considered as independent of specific elemental alignments.

I'm not sure if anyone has any evidence of in-game mechanics to support either possibility (would love to see some).