Making historic tracks accurately is really difficult. When the track is as long as the classic Spa track it is almost certain there will be errors. However, evaluating accuracy is also difficult, especially elevations. How steep a track appears depends on the FOV you use for example.
I watched several pieces of period on-board footage and it is very difficult to judge elevation from these.
I decided to check out this criticism
the approach to Les Combes.. should be uphill, not downwards.
There is something of an optical illusion and it is quite hard to judge if its uphill, downhill or level. The method I used was to bring an open wheel car to a halt. Depress the clutch, release the brake and see which way the car rolled. This showed me the approach to Les Combes is actually uphill on the PC2 track, not downhill as claimed.
I also checked
such a dip at Malmedy.. it was never there..
IMO period footage does show a dip at Malmedy. Is it exactly as in PC2? - can't be sure but there is a dip.