A DVD-Video disc is a data disc with a particular structure: it must have a VIDEO_TS folder at the root of the disc with the *.IFO/*.VOB files inside it, and it must have the UDF 1.02 filesystem. In other burning programs, these requirements are only enforced when you select the DVD-Video compilation/profile.
ImgBurn, on the other hand, recognizes DVD-Video content by the presence of VIDEO_TS.IFO/VTS_xx_nn.IFO/VTS_xx_nn.VOB files and asks/makes the appropriate changes, if any are needed.