In practice
Check what a crawler receives by viewing the raw source, not the inspector — the inspector shows the page after JavaScript has run.
Content that only exists after a user interaction or a data fetch may never be indexed at all.
Why it matters
Rendering is queued and budgeted, so client-rendered content is indexed later and less reliably than server-rendered HTML.
It also delays first paint on slow devices, which is where most mobile traffic actually sits.