It's a bit sad that CGP Grey's promotion of this last year has helped to reduce the amount of available documentation, as (according to one of the few other YouTube videos on hexagonal chess) after this video came out there was a run on what copies of Gliński's book remain in circulation and it's now extremely hard to get hold of any copy at all. I'd be interested in what the book said about openings. It claims to discuss them on the cover. The wisdom for them appears to be quite different to that of square chess, and I wonder how much of that became apparent once people started playing in competitions.

It took about an hour of looking at the rules for me to come to the conclusion that the starting layout makes this a very different game to square chess; despite how much was done with the knight's and bishop's moves to keep it like square chess rather than pick up the hexagonal ball and fully run with it, retaining a diagonal component that really makes little sense when one raison d'être of hexagonal boards is to do away with sqrt(2) distance diagonal moves.

The bishops and queens and even the kings are in play from the first move, making the conventional wisdom of pawn openings a very bad choice indeed for Gliński hexagonal chess. There's a fairly trivial fool's mate in only 3 moves using only the front and middle bishops, not even needing the queens or moving any pawns, which is difficult to oppose using anything less than one's own bishops; meaning that there's greatest incentive to get the bishops into play before anything else. (Bishops turn out to be super-powered. Not even knights are able to get across the board quickly enough to mount a good defence against the fool's mate with bishops.) There are equally good reasons to not move the pawn wall at all, as only rooks cannot escape it and they are useful defensive pieces to retain within the wall, square-chess-style castling effectively having already happened. (The lack of castling is actually fairly irrelevant.)

A bit of thought indicated that moving the starting positions of the middle 7 pawns back 1 cell and moving the rooks's starting positions in towards the centre would make the game more similar to square chess, when it comes to the opening game. McCooey's version of hexagonal chess does this, and since it was invented fairly quickly after hexagonal chess rose to prominence in the 1970s, I wonder whether McCooey saw exactly these problems and fixed them in the obvious way. The fact that it not only limits what's in play at the first move and prevents the mate in 3 possibility but also restores the diagonal captures of pawns (like square chess but as opposed to the axial captures of pawns in Gliński chess) seems to indicate that McCooey wanted things to be more square-chess-like than Gliński's actually turns out to be.

Wellisch's hexagonal chess goes the other way, running with that ball and making things more hexagon-native and less preserving of square-chess norms: doing away with Gliński's knights entirely, effectively renaming Gliński's bishops to knights, and restricting their distances of travel so they aren't the super-powered nuclear offence opening pieces that can give mate in 3.