I concede the short giraffe. As it was a hastey example, it is hardly a pivotal matter. Some giraffe got taller, some didn't, both survived. Sort of negates the supposed advantages of either. See the total supposition works both ways, and is just as scientific.
You are truly stating that biologists don't make assertions about "why" animals developed certain traits? I guess you've never read a textbook or watched a nature documentary. Again, obstinance raises its ugly head.
If only academia were half as scientific as you claim...
Lets review: Variances arise within a species. During fat times, all survive, so combinations of multiple mutations are possible. Genetic variations are base 4 digital and quantum.
During lean times, natural selection gives some species an advantage. Barriers permit some populations to evolve separately from others, even when they may be initially the same populations. For the Giraffe, the longer neck may have permitted expansion to forested areas.
For Humans the difference between 44 chromosomes for other great apes, and 43 chromosomes for Humans constitutes a significant barrier. Barriers can be geographical, chemical, or biological.
Most biologists say things like “may have permitted”. Journalists and even text book writers sometimes drop the weak suppositions. I would suggest that Science is something done in the field, or at universities (or institutions like the Page Museum, close to where I live). Education is something that is done in schools, with a text book. Propaganda is something that is done openly with a microphone, or silently with the censor’s pen or delete key.