Yes, that's it. I've not seen a ligature used that way in text before. English has words that can be spelled with ligatures to this day, but not for the sound "st"

https://en.wikipedia.org/wiki/List_of_English_words_that_may...

Its just a fancy typographic ligature, not a spelling “ligature” (which, in turn, is more of a letter with an optional decomposition as an anti-ligature) like ash (æ) or ethel (œ).