Yeah I figure “experience” is sort of ambiguous and pop science-y, but it’s how I’ve usually had it explained.
That redshift depends on the observer is obvious now that you point it out and profound too since yeah, I suppose they’re not developing across space in the way I imagined.
This makes me wonder about a potential universe with nothing except photons/radiation in it. They’d just.. never change? Even though they could do things like affect spacetime they pass through or interfere with eachother?