No. The colours on CGA composite are a direct result of the high frequency pixel data and the colorburst.
VGA uses a different frequency, so its scanlines are not directly compatible with NTSC. VGA to composite converters capture a frame and regenerate a new signal at NTSC frequency (dropping frames in the process). So they reconstruct the signal entirely. In doing so, they probably take care to filter the signal to avoid any 'unwanted' aliasing. Also, the pixels are unlikely to be the right frequency for the resulting NTSC signal, so even if they would be aliasing, it is not likely to result in the same artifacts as regular CGA.