Unfortunately it isn't that simple. Check 3 only looks to see if we are moving backwards into the station slot. This is a bit pointless to calculate as falling backwards would mean that a number of the other checks (e.g. angle of approach) will already be failing.
This is why check 3 is omitted from later versions of Elite, including the C64 version; it isn't needed.
Besides, is this a bug or a feature? Elite lore says that machine intelligence is banned in the galaxy, so I like to think of this as fitting in with that. Docking computers can kill you in Elite - and it's the same in Elite Dangerous. :-)
This is why check 3 is omitted from later versions of Elite, including the C64 version; it isn't needed.
Lots of information on the docking checks here:
https://elite.bbcelite.com/deep_dives/docking_checks.html
Besides, is this a bug or a feature? Elite lore says that machine intelligence is banned in the galaxy, so I like to think of this as fitting in with that. Docking computers can kill you in Elite - and it's the same in Elite Dangerous. :-)