You seriously think that’s what the pdf timetable shows? The last journey from Walthamstow Central to Liverpool Street is at 2334. The four journeys in the timetable after that come from the Lea Valley line (e g from Stansted Airport) and are only there for convenience because they offer later journeys from Seven Sisters and Hackney Downs (only). They are Greater Anglia trains going nowhere near Walthamstow Central.
Yes, the map (mainly the timetables, actually) needs splitting into separate lines. It’s a lot easier to see what’s really happening without the other lines adding confusion.
I can understand that LO might not want the expense of printing and distributing three separate timetables in stations. But that’s no excuse for not making the three PDFs available for download, which would cost almost nothing once a system had been set up to export those PDFs automatically.
The only real “excuse” for not making separate PDFs is that if LO did that, people might then ask LO to distribute pre-printed copies of them, and that would represent a small cost to LO.