What's the purpose of depiction of visual flight track on some Jeppesen approach charts?
From the Jeppesen chart legend PDF:

Visual flight track is shown when the missed approach point is prior to the runway threshold.

So this depiction is when the MAP is before (and not at) the threshold.

FAA style:
(airnav)
It's quite hard finding an early MAP, but here it is above as depicted by the FAA. It means to expect a visual segment as shown above when/if continuation below the visual descent point is not approved.
I also found this very nice read: Where To Start The Missed Approach