@Silfir You're not wrong, but the manga's chess realism was already on shaky ground with the "oops I didn't know about castling so my certain victory has become certain defeat" from a supposed prodigy character. We're just going to have to put chess rules in the suspension-of-disbelief pile for this manga.
Maybe this makes more sense to a writer who was assuming chess works like some other game where this is realistic. Shogi maybe?
To be clear, walls of text talking about nothing but the chess in any given manga chapter on mangadex is the one truly self-indulgent pastime I allow myself. It's not serious at all.
Obviously the mangaka is a little hamstrung by the light novel they're adapting, where most of this chess talk originates from. The one piece of research that I think they should be able to do, though, is to watch the anime. Assuming we're caught up to the raws, they should be able to steal the homework the anime production did for the upcoming chess content.
I wish I did know a little more about shogi, so I could put this stuff into the proper context. The thing is, I thought there was something about stalemates being more common in shogi, but a stalemate by the definition of chess (no legal moves) is even harder to come by there than it is in chess, because players can put captured pieces back onto the board. Also, a stalemate in shogi is a win for the player who delivers it. So maybe during research the author of the light novel found out that stalemate in chess is a draw (unlike in shogi), and that a draw is the most common outcome for a game of chess, and thought one fact had to do with the other.
(What I was thinking of with regards to shogi having more stalemates was
jishogi, translated to "impasse". Most shogi pieces are rubbish at moving backwards, so when the player's kings reach their respective promotion zone - the other player's starting zone - a draw by impasse is usually declared if both players have roughly the same amount of material. But like all forms of draw in shogi, an impasse is extremely rare to come by. The rules are basically designed to force a result. So it may be hard to understand for someone with purely a shogi background exactly why chess has so many draws.)
I don't want to hate on the chess in Silent Witch too hard, because a lot of it is fixable if you substitute the term "stalemate" for just "draw". The truly unforgivable crime is Elliot's refusal to promote, which gives me far less to talk about because it's so obviously wrong. And it makes no sense in shogi either, so there's a distinct possibility the author knows jack about either chess or shogi.