First, The Chessmen of Mars was first published in February-March of 1922. The dates you give was the period when Burroughs wrote the book.
Second, the appendix was not added to the first edition book; it was there in the final instalment of the original Argosy publication, and was probably written first, even before Burroughs got started on writing the novel as such. Thus, the appendix rules are not to be seen as an afterthought or a revision, but as the original. Whether the jumping thoat from Chapter two was a mistake, or if it was mistakenly left out of the appendix, or if it was an actual case of a revision, we shall never know.
A couple of comments to George Duke:
First, The Chessmen of Mars was first published in February-March of 1922. The dates you give was the period when Burroughs wrote the book.
Second, the appendix was not added to the first edition book; it was there in the final instalment of the original Argosy publication, and was probably written first, even before Burroughs got started on writing the novel as such. Thus, the appendix rules are not to be seen as an afterthought or a revision, but as the original. Whether the jumping thoat from Chapter two was a mistake, or if it was mistakenly left out of the appendix, or if it was an actual case of a revision, we shall never know.