The claim
Content that depends on client-side JavaScript can be indexed late or not at all if rendering fails, resources are blocked, or critical content is not present in the rendered DOM.
What the evidence shows
Google's JavaScript SEO documentation explains that Googlebot processes JavaScript in a separate rendering stage and that content requiring successful rendering can be missed if scripts fail, are blocked in robots.txt, or rely on user interaction. Server-side rendering or hydration of critical content reduces this risk and speeds indexing.