WT stores multiple versions of data to support different readers in the system. According to the reader snapshot, it returns only the data that is visible.
As you said when the page gets evicted to disk, the latest version of data is written to the page and all the historical versions are saved in a different table called the history store.
Whenever the old reader requests to re-read the same data, WT internally fetches the data from the history store and returned. Applications don't see different data compared to the first read.