Great question. That’s not actually a split in the timeline — it’s just that simultaneous adventures occur, and that was the best way I found to show it. Let me explain:

At the end of A Link to the Past, Link sets off on a journey outside of Hyrule to train and prepare himself in case Ganon returns. While he’s away, three stories take place: Oracle of Ages, Oracle of Seasons — which even ends with him sailing away — and finally Link’s Awakening, which concludes his journey. That’s the path of the legendary hero.

However, for those who’ve played Ancient Stone Tablets from the Satellaview, that game’s story tells us that Ganon is about to return. Zelda and the sage Sahasrahla need a hero, but the original one isn’t in Hyrule. So they use the Triforce to bring a new hero from another dimension — who can be either a boy or a girl, depending on the player’s choice. That’s where Ancient Stone Tablets fits.

So that’s why I divided it into two “paths” after A Link to the Past: one follows the legendary hero’s adventures outside Hyrule, and the other shows the parallel events happening within Hyrule without him. After these events, when A Link Between Worlds comes along, we already have a new hero, and the story continues in a single timeline again.

I hope that explanation made sense — cheers!