Did Arrian and Pliny believe the sun sets into a spring?

Going through the posts on another forum (r/AcademicQuran), one of the mods made an intriguing assertion claiming that Arrian and Pliny the Elder believed that the sun sets into a particular spring in Trogodytis, eastern Libya.

I past below the quotation in full:

After all, there was a belief that the sun set into an ocean or even a "spring" and that the spring was hot because of the sun itself.

For example, Arrian wrote:

Link:
https://www.reddit.com/r/AcademicQuran/comments/1m7sfc2/comment/n4ucguo/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

When further questioned about whether Arrian really did believe the sun sets into this spring, the moderator responded:

You missed the beginning of the quotation which elaborates on a spring that is "quite unlike all the other springs which issue from the earth", which is what is being referred to later as what the sun sets into, by Arrian.

This is standard in Greco-Roman texts. Pliny the Elder wrote something similar: "The swamp of Jupiter Ammon is cold by day and hot at night. A spring in Trogodytis called the Fountain of the Sunis sweet and very cold at midday, but then gradually warming, towards the middle of the night it becomes spoilt owing to its heat and bitter taste." https://topostext.org/work/148

One can imagine what this "spring", which is known as the "Fountain of the Sun", is for.

Please may I ask for confirmation on whether this portrayal presented by the moderator of r/AcademicQuran is an accurate representation of the worldview of Arrian and Pliny?