It absolutely is not real, or at least it's not a real Microsoft product. 8.1 was never released on floppy.
It's possible that this is a bootleg release targeting an emerging market somewhere. You can use the Windows DISM tool to split the Windows image file (WIM) into split files. Just have the first disk format the target drive, set up a temp folder, run a process that'll wait for each disk to be inserted and copy over the split file when it is, then finally start the installation command when all have been copied over.
Legacy system operations are used to slow processes. So I don't think it would matter that it would take days.
I agree; I don't think it's real. What system is too delicate to install an optical drive and yet you still have the need to install a "new" OS? This kinda assumes that any system that could run Windows 8 can handle an optical drive. I'm kinda hoping to be schooled in some corner case that would warrant this.