This may be more specifically a Herolab issue, but I am unclear as to whether the mechanics truly work like this…
In trying to build an Aasimar, I added Scion of Humanity. Doing this (in Herolab) opens up all of the Human racial traits in the UI. This is the first point in question: "should this happen"? The only statement I've found (of use) through googling is this guy who states:
They can count as "human" through the Scion of Humanity race-trait,
which opens up most EVERYTHING that a 'human' would have access to
(i.e. a feat which lets 'humans' count as any other race for
starters).
Hinging on that, I was able to add Dual Talent, a human racial trait, which states that "This racial trait replaces the +2 bonus to any one ability score, the bonus feat, and the skilled traits." Aasimar start with Skilled, so that applies, but a bonus feat (as humans have) never appeared when taking Scion of Humanity, so this becomes a little sticky: how does one replace that which you don't have?
The third issue is that with Aasimar heritages, which function nearly identically to the Dual Talent in that it adds +2 to two different Abilities. Compounded on this is the Aasimar Abilities, which beyond basic Skill modifiers, also allows you to add +2 to one Ability.
Assuming you wanted to amp Strength, this adds up to a total of +6 Strength without spending a single Ability point. This feels wrong, but (by golly) sure would be nice if it's true.
Can someone clarify?
Best Answer
The aasimar alternate racial trait scion of humanity can't grant access to human alternate racial traits
Up front: Don't confuse race traits with racial traits. Human (and aasimar) race traits are what the aasimar now qualifies for because of the alternate racial trait scion of humanity. On the other hand, racial traits are those specific facets of the creature's race that can be picked and traded for other facets of the creature's race because of the creature's race.
So, although the aasiamar has picked the alternate racial trait scion of humanity, the aasimar's race nonetheless remains aasiamar. Hence, an aasiamar that takes the alternate racial trait scion of humanity can no more pick human racial traits than a half-orc can pick human racial traits. An aasimar with the alternate racial trait scion of humanity could take as its two race traits Aspiring Bard and Bralani's Step, but the same aasimar couldn't take the human alternate racial traits heart of the sea and heroic.
So while the alternate racial trait scion of humanity says
...this alternate racial trait doesn't give the aasimar anything the aasimar didn't already possess. Herolab shouldn't've allowed such an aasimar to pick the human alternate racial trait dual talent, first, because the aasimar's not a human, and, second, because the aasimar doesn't have the things the alternate racial trait dual talent needs to replace. That is, the alternate racial trait dual talent says that it
And the aasimar, even if the GM allows the aasimar to take human alternate racial traits, doesn't have those other traits to trade away for this trait, making the aasimar ineligible for the new human trait, just as the aasimar would be ineligible for a feat that had as a prerequisite human and Str 70 (assuming the aasimar didn't have Str 70, obviously). Even were the aasimar to meet the human prerequisite—which it does—, it can't meet the remaining prerequisites.
Aasimar variants' ability score bonuses replace the typical aasimar ability score bonuses
That is, an aasimar gets either the typical ability score bonuses or the ability score bonuses for the variant he rolls or picks:
Emphasis mine.