Question on Me'am Lo'ez source

Question

In the English translation of Me'am Loez, Shemos, Ki Thisa, Chapter 10, verse 33.11, the Meam Loez explains why Yehoshua was named bin Nun, and not ben Nun. He says that when Joshua's name was changed from Hoshea to Yehoshua there were no nekkudot for the yud, (which had been previously part of the name Sarai before a yud was removed and replaced with a heh, making Sarah [BT Sanhedrin 107a]) so two dots were "borrowed" from the segol under the "ben," leaving it with one dot, that is, a hirik. The footnote for this source says it is from Baal HaTurim, parashas Shlach. However, I could find no such Baal HaTurim. I saw online that it was brought in the name of the Chasam Sofer, but the Meam Loez on this part of Shemos was published in 1746, before the Chasam Sofer was born. Was this then not part of the original Meam Loez? Thanks.