He [i.e. the king] is royal, but can't be captured by displacement, he simply must avoid check.
Presumably this precludes Qe8; as I understand it, the proposed defense thus prevent capture of the defending piece on e7 (which could also be a knight) by having the square after it not be vacant (it's occupied by the king) whilst blocking the check (which is “as in chess”) as a Chess rook would be unable to capture the king.
Iow one can't ‘displacement‐capture the king’ (for the purposes of calculating Check) and capture anything else in the same move (except with a knight).
This whole checking‐differently‐from‐capture business is rather confusing
Presumably this precludes
Qe8; as I understand it, the proposed defense thus prevent capture of the defending piece one7(which could also be a knight) by having the square after it not be vacant (it's occupied by the king) whilst blocking the check (which is “as in chess”) as a Chess rook would be unable to capture the king.Iow one can't ‘displacement‐capture the king’ (for the purposes of calculating Check) and capture anything else in the same move (except with a knight).
This whole checking‐differently‐from‐capture business is rather confusing