cinelerra

Something I have problems to understand, some how I got very good deinterlace. I did not deinterlace in Cinelerra, I used QT to do this.
Cinelerra is excellent NLE, but not a good format converter. I use other machines like on iMac - QT, ffmpgX, MpegStreamClip. This video clip - capture (Linux Gentoo)
1.DVGRAB (720x400 dv) -> Cinelerra -> set format 1280x720 -> render -> yuv2.mov.
2. yuv2.mov -> Cinelerra - scale x=1.777 y=1.52 -> format 1280x720/16:9/25 fps -> render -> yuv2-scale.mov
3. yuv2-scale.mov -> (iMac)QuickTime 7.6 -> export 25fps/deinterlace/h264 -> Cinelerra-720p.mov
When played yuv2-scale.mov looks like there is no interlacing, why?????
Resulting film is in 720p, deinterlaced - quite good actually.