The editing function is more than enough but the problem is that you do not see the video and therefore it is not usable (I'm under Windows 10 64 bit 19H1)
https://i.postimg.cc/44tQLRHL/immagine.png
As for the fact that sources are hardly at 50/60 fps real is certainly true but with Hdmi acquisition cards this is possible (or in my case a sender Hdmi that using multicast, I wrote a
utility to grab it with ffmpeg). Avstodvd developers could add a check as for the DV source confirming manually that the source is at 50/60 fps real and set the proper avisynth script