Battery voltage compatibility
My best guess is that the camera manufacturer simply chose not to include the fractional voltage in the battery rating.

Older Li-Ion batteries are 3.6V nominal with a max charge voltage of 4.1 Vdc.

Newer Li-Ion and Li-Poly batteries are 3.7V nominal with a max charge voltage of 4.2 Vdc.

Your original battery most likely has 2 Li-Ion cells in series to make a nominal voltage of 7.2V.

Note that you may want to use an after-market charger if you are replacing the battery with a modern equivalent.  The new battery won't be damaged by the old charger but it may not exhibit the full capacity because it doesn't become fully charged.