Interlacing was normal
A lot of old camcorder and tape footage was recorded for televisions that displayed fields rather than full progressive frames. On modern screens, this can show up as comb-like horizontal lines around motion. It is not necessarily a bad transfer. It is often how the source was stored.
Why it must be handled early
If interlaced footage is sharpened or upscaled before field handling, the combing gets larger and more visible. Proper deinterlacing rebuilds progressive frames so the rest of the restoration pipeline can work on a cleaner motion structure.
The details matter
The operator has to check field order, cadence, duplicate frames, dropped frames, and motion consistency. Some sources can support a smoother progressive output. Others need a conservative conversion to avoid blur or artificial motion.
What customers should expect
Good deinterlacing makes old footage easier to watch on laptops, phones, and modern TVs. It does not magically create camera detail, but it prevents motion artifacts from ruining the later denoise and upscale steps.