Why does my named pipe keep getting modified?

I have a named fifo created from a C program like this:

res = mkfifo("/home/myfolder/myfifo", 0666);

after that there are only reads and writes.

Now, from this answer : Does a named pipe change the filesystem I concluded that the system should practically never actually write in the actual file on the filesystem, and that everything is handled in RAM.

Whenever I restart my program, the “mkfifo” line returns a “File already exists” error, which is OK.
What bothers me is that when I “ls” the file, the “last modified date time” sometimes does change. If the system never actually writes into the file, shouldn’t it remain constant?