Thanks for finding that source! I was looking at the list of floppy disk formats on Wikipedia to respond, and it didn't have that.
80 cylinder, 96 TPI
This was the second type of 5.25" drive made, and the least popular (and known) of the three types of drives. These double the capacity of the original drive by doubling the number of cylinders (tracks) from 40 to 80. They use the same media as the the 40 cylinder 48 TPI drives, but it is certified (tested) on all 80 tracks, as opposed to the standard disks which were only certified at 40 tracks.
These drives were never common on PCs, although DEC used a single sided version called the RX-50, in the DECMate word-processor, the DEC Rainbow and several other DEC computers, including the PDP-11 and the VAX.
Other than the DEC RX-50, these drives were almost always double sided, and recorded in double density MFM. They had a capacity of around 720K. Like the 40 track drives, they used 300oe media, and the drive rotates at 300 RPM
So apart from one very rare example, if you're talking 5.25" disk floppies, 360K meant double-sided. I expect the vast majority of people cutting out the notches to flip over their disks were using Apple II, Atari, or Commodore computers. In that realm, 90K was SS/SD and 180K was SS/DD. Most users didn't have double-sided drives until the IBM PC started using 360K DS/DD disks.