In the Talent listing on p. 100, it indicates that Falling Avalanche adds damage to one hit of a successful Lightsaber combat check.

In the Sentinel: Shien Expert specialization tree, it indicates that Falling Avalanche adds damage to the next Lightsaber combat check made this turn.

These two are very different. In the first one, it seems the player can make a check, and if successful, take 2 strain to add damage. In the second one, it seems the player must decide before making the check, and takes strain damage even if the check fails.

In general, what appears in the tree is just a summary; it's what's in the Talent listing itself that's authoritative. Very often the talent tree doesn't give you the full picture.

Yes, I think the Talent Listing is authoritative, but in this case the description in the tree is too different. One of the two is wrong.

Given the choice, I'd take the one in the Talent List, since it seems more in-line with other talents that add damage to one hit of a successful attack.

They're really not that different. The one in the tree leaves out the word "successful". The descriptions in the talent trees are just supposed to give you a quick overview of what the talent does; it's not authoritative. The talent description in the talent listing is.

Tree: "Suffer 2 strain to ... add damage to next ... combat check made [this] turn."

vs.

Listing: "may suffer 2 strain to add additional damage ... to one hit of a successful ... combat check."

Are entirely different. It isn't the case that the one in the specialization tree is a shortened version, because it has extra verbage that indicates the strain is taken before the combat check is made. The one in the talent list follows the normal pattern, which allows the strain and additional damage to be decided after the hit has been calculated.

I'm not writing this to provoke argument: there's nothing to discuss; it is how it is written. I'm writing this so that people are aware that the version in the tree is not the same as the version in the talent listing, and they will have to choose how to have it work in their game.

Good catch. I imagine the talent description is correct, and the one in the tree would need to be edited.

You should probably cross-post in the Proofreading forum, then, so the devs know to update it.