I recently had exactly this issue in another project DS3231 Service Tool where I was entering data manually via the Serial Monitor.
There the line ending setting really mattered, because pressing Send could append \n, \r, both, or nothing, and my receiving code had to deal with that accordingly.
But I think that actually illustrates @UKHeliBob's point here: that was a manual Serial Monitor input problem.
In this project the data is sent automatically from one MCU to another. So the Serial Monitor line ending setting is not involved at all. What matters is simply what the transmitting code actually sends and what the receiving code defines as the message terminator.
Edit: If the MCU is the sender, as in my project SerialLED, there is of course no Serial Monitor line-ending setting involved. The transmitting code itself defines exactly which line ending is sent.