I know I've installed Win95 off of floppies. Don't recall the exact number, but believe it was around 40-50 3.5" floppies. It came in a box about the length of a shoe box.
Now I know why.
https://i.imgur.com/iVNVleR.jpg
The media I copied from took up 28x 3.5" HD floppy disks. It's possible they were copied from what was originally a CD-ROM. I don't remember clearly anymore.
Note: I'm not trying to refute or correct your 13-disk figure, which was clearly a different installation set, and likely original Windows 95 rather than my OSR2, which came out around 1997.
[0] https://devblogs.microsoft.com/oldnewthing/20050819-10/?p=34....
Edit: just checked in Google. Win95 was just 13 floppies. But you had MS Office and other software that was additional floppies to install.