The article is rounding up, and the parent comment is talking about Voyager 1.

Specifically: Voyager 1 is 23.8 billion km (23.8 Tm), and Voyager 2 is 18.3 Tm.

For those that might not be aware, Voyager 2 launched before Voyager 1, so the distance discrepancy is not due to the further one being launched first

Voyager 2 was launched first but on a less direct trajectory out of the system which allowed it to visit Uranus and Neptune. Voyager 1 is going much faster

https://voyager.jpl.nasa.gov/mission/status/

There is an effect called dispersion, which causes different frequencies of electromagnetic radiation to travel through a medium at different speeds (lower frequencies => slower).

It's strong enough to be noticeable in the case of pulsars (but probably insignificant inside the solar system).

I think it's because space isn't a perfect vacuum. The interstellar medium is a mix of gas and dust that slow down and weaken the signal. That effect is known as dispersion.

With that said, it seems like the article might be inaccurate. That discrepancy seems too large to be explained by dispersion. I'm not an expert though.

edit: I think the author got Voyager 1's distance mixed up with Voyager 2. Voyager 1 is ~22 (21.6) light hours away.

Sounds more like ChatGPT got it mixed up.

Don't confused TTFB with message transport time. With a low bandwidth link, throughput becomes part of latency. Probably not 3.5 hours, but some fraction of that.