Which is a wrong term choice, indeed.
As we are playing a game which contains RPG and Puzzle in his title, shield is something that is recalls the concept of a shield item (so a item you use to increase your defense) [for example: “Paladin wears a shield”]. So using the world “shields” can be confusing and can be easily misunderstood by players.
I think that a game, while introducing his own terminology, should remember the commonly used game terminology.
So, backing in my example, if I say “Paladin wears a shield” I understand that Palading has a shield (in a hand) that will cover part of body. But if a game, for example, will call “shield of tempest” a mage staff, it would introduce terms confusion, even if the entire game uses the terms “shield” to identify all the mage staffs in the game and even if the entire game does not use the word “shield” in any other content.
I can agree that the term “tile” could be arguable too (for example, in game design, the tile is a portion of a design unit to fill a map terrain with a certain type of terrain/decoration).
But, again, the concept of “tile” is also tied, in the common sense, with the concept of “piece”. You can have “tile” of puzzle (which is a piece of puzzle) and those units in board (since the game calls itself also “puzzle”) could be considered piece of this puzzle, so a tile.
However I proposed the term “tile”, but another term could be good too, as long as it does not introduce confusion. But “shield” imo need to be changed: it is a term that has a common meaning too different from the one intendet, so it is very confusing term to describe “piece of board” imo.
PS: Ratatoskr is a new hero and probably his description inherited the same concept, you are right. But, imo, simply means that it was used a wrong world in multiple place (read “wrong” as “term that introduce confusing concept and have high risks to be misunderstood by players reading it”)