Lathliss, Dragon Queen + Where Ancients Tread interaction
The table is correct.  Lathliss will not buff Dragons that enter the battlefield after the ability has resolved.
Lathliss' ability produces a continuous effect that buffs your Dragons until the end of the turn.  Part of generating this effect involves determining the set of objects that it will affect.  From the Comprehensive Rules (emphasis mine):

611.2c If a continuous effect generated by the resolution of a spell or ability modifies the characteristics or changes the controller of any objects, the set of objects it affects is determined when that  continuous effect begins. After that point, the set won’t change.

Since Lathliss' ability has already resolved before you play Scourge of Valkas, Scourge won't be affected by that ability.

The situation with Honor of the Pure plays out differently, because its effect is produced by a static ability.  Again from the Comprehensive Rules:

611.3a A continuous effect generated by a static ability isn’t “locked in”; it applies at any given moment to whatever its text indicates.
611.3b The effect applies at all times that the permanent generating it is on the battlefield or the object generating it is in the appropriate zone.

So Honor of the Pure will buff any white creature that enters the battlefield, as well as any creature that becomes white, or any white permanent that becomes a creature.  Conversely, if a creature somehow stops being white, it immediately loses the Honor bonus.