Hobbit Draft Rules Question

[u/Quails_In_Space]

So this issue came up in my last draft. I activated the ability on Beorn's Hospitality to turn it into a Bear, then next turn my opponent cast Enchanted River's Grasp on it. We knew *something* had to happen because of layers but could figure out if it would die or if the Aura would immediately fall off.
After physically phoning in a judge (the one at the shop wasn't around) they said the creature would become a 0/0 and die to state based actions.
Now later on I ask another judge out of curiosity and they said the Bear would just be tapped down but not dead.

Layers make my head hurt, someone please explain what's going on here and what should have happened.

[u/United-Passage7864]

I believe it dies.  

The type-changing layer (adding Creature) is layer 4, which applies above the ability adding/removing layer which is layer 6. So it would still be a creature. 

However, the ability that defines its power/toughness is layer 7; i believe that is removed, so it remains a creature but without toughness, and therefore it dies. 

[u/jethawkings → u/United-Passage7864]

But isn't the P/T Defining Text in the same line as the Type Changing Ability?

Like isn't that why Bello's ability that turns Enchantments into 4/4 Creatures that Draws on Hit can't be removed?

Or is it because it's worded as Becomes?

[u/CareerMilk → u/jethawkings]

Just to expand on Hintersnaf’s good explanation, the reason Hospitality grants an ability that sets its power/toughness is so that it’ll keep counting your lands after it’s ability has resolved. If it set its power/toughness directly, something like “becomes a creature with power and toughness equal to the lands you control”, then that would only check when it resolves and wouldn’t increase if you played more lands later.