The game is larger than the mechanics. The art is part of the game on a basic level, alongside the mechanics. The art can inspire a player or DM and have an impact on a campaign in that way, directly, without necessarily being representational or derivative of the mechanics.Why are these issues for the art if they're not also issues for the game? The art doesn't exist in a void, it is a visual representation of systems, rules, points, suggestions and themes within the books.
The game is larger than the mechanics. The art is part of the game on a basic level, alongside the mechanics. The art can inspire a player or DM and have an impact on a campaign in that way, directly, without necessarily being representational or derivative of the mechanics.
Of course coherence is important...the art shouldn't depict something completely impossible by the mechanics of the game or something like that. But the position you are taking here is far too strong.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.