I disagree. I understand the purpose of this statement, i.e. not to discourage people, etc. but clearly there are differences between Terry Tao, Wiles, Feynman, and many others and your typical PhD in these fields. This is like saying anyone can become Phelps with practice (although pinpointing his unique advantages can be complicated: https://www.scientificamerican.com/article/what-makes-michae...). Not everybody can be above average! And of course, there are the rare cases such as Ramanujan.
I think a better explanation is the one that Stephen gives in On Writing:
"I don’t believe writers can be made, either by circumstances or by selfwill (although I did believe those things once). The equipment comes with the original package. Yet it is by no means unusual equipment; I believe large numbers of people have at least some talent as writers and storytellers, and that those talents can be strengthened and sharpened."