[Alex KL-1]

I dunno about this circuit in particular but, in most cases, this is a video amp signal with insufficient bandwidth (this is common with newer TV's with outrageously high 15k video amp load resistors).
Sometimes makers opts for lower bandwidth for making noisy or grainy images less obtrusive to users.

I have an 16" Toshiba from 80's with those 15k video amp load; I put another 15k in // and readusted bias etc. Far better sharpness from the video input (I added a S-Video input). But if we want too high video response, things like Y delay coil ringing starts to appears, so a compromise is needed, since all of this is calculated for the reduced bandwidth from a composite signal.

Ah, I see some probably ringing also, besides the probably response limitation.

Also, if you are using antenna input (I suppose), the IF response can influence to a certain point.