What's your definition of "strongest"? In terms of success measured by exit size, it's empirically untrue. Perhaps if you are measuring by failure rate, but even then, I doubt it.
FWIW, it can't be empirically true either. :-)
What I am saying is that starting off one's journey by taking money or going through an accelerator enters you into an efficient machine for building a startup in a specific way.
From what I have observed, entering this path often traps founders into thinking this is the one true way to build a startup. In reality, the paths to product-market fit are unknown. You often discover them through serendipity. Being rigid can cause you to miss them.
I am not saying a startup should never take money. Once a startup has discovered their magic, i.e. achieved product-market fit, then taking money and using it to scale is the right way to go.