It is as simple as this.
If one or two C 919, god forbid, go through any problem or mishap, then Chinese themselves wouldn't travel in the plane.
And XJP himself will be happy to scrap the plan to force C 919 on them.
I am not saying that the huge domestic market doesn't give favorable conditions to Comac.
But winning trust and confidence as a world class jet maker must come from the quality of the product, or else, no Communist Party Leader will be able to force people on to the plane.
I don't think what gamble says and what you say are in any way different.
What he is saying is that C 919 and Comac in general will require credibility and reliability. Any passenger will be skeptical of flying in a new jet, built by a company that is relatively new. Also, China doesn't exactly have best of reputations, even within the country itself, where people still value foreign brands and products.
So, that is right. But once, the jet is reliable and safe, then what you say is right. That China can leverage its huge market to get a head start to Comac.