This one is very similar to the Legend Rule update. Previously, any two planeswalkers on the field with the same subtype would go to the graveyard immediately. Now, the game only looks at the planeswalkers controlled by the same player, and if there are two or more with the same subtype, the controller chooses one to keep and the others go the the graveyard.
What does this mean for you? Well, Jace Beleren no longer kills your opponent’s Jace, the Mind Sculptor. Also, you and your opponent can both have Jace, the Mind Sculptor at the same time, rather than racing to be the first to resolve one. And if you control Jace Beleren when you cast Jace, the Mind Sculptor, you can choose to lose only Beleren while keeping the Mind Sculptor.
Additionally, you can cast a planeswalker such as Liliana of the Veil, activate her -2 ability, then cast another Liliana of the Veil. You can choose to keep the new one and put the old one in the graveyard (rather than losing both), and then you can activate the new Liliana’s -2 ability.
Looks like only one older tip needed to be updated for this change:
Planeswalker Names and Subtypes
Today’s Rules Tip written by Josh Stansfield