With other greats we can say, at most "He had a head start running to school 10K each way", or maybe "His dad was on an Olympic relay" yada yada. Mostly we can speculate about how optimal their youth was etc, but we will never know for certain.
But with Jakob we have these certainties or near-certainties:
1) Proven world class genes
2) A perfectly ramped progression from age 10 if not younger with very little downtime from injuries.
3) No barriers of funding, finding a good fit for coaching, getting in to the right meets, etc.
I.e. Perfect logistics
Add to this the fact that if ANY of the I-brothers were busted or suspicious (keeping in mind that they have been more transparent to media coverage in their very homes than any runners in history), ALL of them will suffer the judgment of the running world. Not a whisper on this front, other than the usual "He runs too fast" here on LRC with zero objective evidence.
No reason he shouldn't be the best of the best.