Orcs, Elves, Humans are same species. Proof? They can mate with each other and produce off-spring. Half-elves, half-orcs.
From Wiki: "A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring".
So we have within same (same) combined specie of Humans-Orcs-Elves some groups, which are called "race" (which is already troubling since "Although still used in general contexts, race has often been replaced by other words which are less ambiguous and emotionally charged, such as populations, people(s), ethnic groups, or communities, depending on context" from Wiki).
Going further, from science viewpoint telling that "race" (or more politically-correct: ethnic group) Half-Orcs have more Str and less Int then people of Elvish origin, is like saying - for example - that Afroafricans have more Str and less Int then for example people of Jewish origin. (Since all of this ethnic groups belong to same specie, Afroafricans and Jews to Humans and Orcs-Elves-Humans to same specie, example is correct).
Of cause, some can argue that there can be high Int and low Str Half-orc, same as can be high Str and low Int half-Elf.
Problem that as whole typical HO would still be stronger then typical HE. And second problem is that from birth some ethnic group have some advantages/disadvantages which contradict "all groups are equal in everything" axiom.
Is it troubling for you?