For the sake of science:

Microsoft historically used the 21 512 byte sector, 80 track, double-sided DMF format for 3 1/2" Windows installation media, yielding 1,720,320 bytes per floppy.

Assuming this format, floppy requirements for the four Windows 10 21H1 variants currently on MSDN are

  x64 Consumer (Home/Pro): 3,398 floppies
  x64 Business (Enterprise/Education): 3,323 floppies 
  x86 Consumer: 2,416 floppies
  x86 Business: 2,361 floppies

Assuming the "1.44 MB" (18 512 byte sector, 80 track, double-sided) format, you'd need

  x64 Consumer: 3,965 floppies
  x64 Business: 3,876 floppies 
  x86 Consumer: 2,819 floppies
  x86 Business: 2,755 floppies

In this case, assuming the most popular (x64) platform, you'd actually need closer to 4,000 floppies.

Assuming ideal 500 kbit/sec performance and two seconds per disk swap, reading 4,000 "1.44 MB" floppies (or DMF floppies with equivalent data) would take just under 28 1/2 hours.

So you could easily install any Windows 10 21H1 version from floppies in the course of a single work week, with enough time left over, perhaps, to check Windows Update over a 56 kbps modem (though you'd probably need the weekend, at least, to actually download the updates).

The random seek time would be brutal though.

The Windows install floppy disks almost always came on DMF formatted disks which hold 1.68mb of data. That saves you about 350 floppies.

Fyi: that is as far as I know the reason for most oldy cab installation files being that size.