Exactly. A halfling who trained his whole life for strength will be stronger than the common half orc (highest score in strength), but weaker than a half orc which did the same kind of training (lower strength than a half orc who also put the highest score in strength because of racial modifiers).
The halfling needs to work harder (put more ability increases into strength) to match a half orc.
Thats how it is -before- Tasha's.
I still don't agree that it must be so.
a) If it is accepted that an Elf (or Halfling, or Lizardfolk) can reach 20 Strength, and that it is seen as representing the fact that they trained, then I don't see why it would be a problem to say that the Elf trained their whole life, hence why they now have 17 Strength.
b) The key word in what you say is
common. I think that's where it really all is.
A Half-Orc who similarly trained their whole life, could end up with "only" 16 Strength. Because while they had the same amount of training (possibly training with the above Elf, same teacher, same everything), that Elf just had a leg up on that Half-Orc at birth.
The 17-Strength Elf might be in the top 1% strongest of Elves, while the 16-Strength Half-Orc was only in the 5% strongest Half-Orcs, but not the top 4% (and definitely top 1%). That 17-Strength Elf is thus more exceptional. An equally rare Half-Orc would have 19 Strength.
c) To take an example from Teams & Tournament, I could decide to play a Female East-European. The signature ability of the Basketballer class I want to use is Dunk, which works better if I have a Height of 2m or more, so I'll have a 2m tall Female. Of course, a 2m tall Female is rare. A 2m tall Male is rare too, but less rare. Maybe my 2m tall Female is as rare as a 2.15m tall Male. That's fine.
Judging from real-life basketball, a large number of Males who are
adventurers Pro-Player Basketballer are under 2m in Height, while some Female Pro-Player Basketballer are above 2m tall.
Custom Origin doesn't modify the lore, it only modify the degree of statistical rareness of the characters you can create.
