Oh, yeah, $ man mount.ntfs mentions that:

  Windows hibernation and fast restarting
   On computers which  can  be  dual-booted  into  Windows  or
   Linux,  Windows  has  to  be fully shut down before booting
   into Linux, otherwise the NTFS  file  systems  on  internal
   disks may be left in an inconsistent state and changes made
   by Linux may be ignored by Windows.

   So,  Windows  may  not be left in hibernation when starting
   Linux, in order to  avoid  inconsistencies.  Moreover,  the
   fast  restart  feature  available on recent Windows systems
   has to be disabled. This can be achieved by issuing  as  an
   Administrator  the  Windows command which disables both hi‐
   bernation and fast restarting :

          powercfg /h off

   If either Windows is hibernated or its fast restart is  en‐
   abled,  partitions  on  internal  disks  are  forced  to be
   mounted in read-only mode.

And then:

   remove_hiberfile
          When the NTFS volume  is  hibernated,  a  read-write
          mount is denied and a read-only mount is forced. One
          needs either to resume Windows and shutdown it prop‐
          erly,  or use this option which will remove the Win‐
          dows hibernation file. Please note, this means  that
          the  saved  Windows session will be completely lost.
          Use this option under your own responsibility.

Good catch. If you're right about this being the cause, then my suggestion above about mounting read-write will probably just result in another read-only mount (though I bet that mount.ntfs will print something about a read-only mount being forced in the console).

Good odds that OP just needs to fully shut down Windows, rather than suspending it.

I am going to specify in the body of the post that this is a drive I used as library drive only for Steam, it is not the one holding the Windows boot.

Would that change things?