Line level also applies to NTSC analog video signals whether composite or S-VHS (chroma a luminance delivered independently). It is a very handy designation to distinguish between the varying analog voltages and their RF modulated counterparts.
In all of my years working in the TV industry as a working professional. Doing up links, utility work, working as EIC on many trucks and many programs, I have never heard of video signals called line level.
ONLY AUDIO! We always called it by what it was, ie
Composite, SDI, HDSDI, ASI, 3G, fiber ect. On some of these trucks if you were caught saying that you would be kicked off site and never hired again as a freelancer. Infact, even in TV school it has always been called composite signals when referencing NTSC Analoge video signals. If you would like to learn more here is a great resource.
http://www.productionapprentice.com/tutorials/general/component-composite-and-digital/