The rules of the Exec club state, among other rules, that -

15.12. Rewards for travel will only be issued to and from destinations served by British Airways and/or Airline Partners designated at the time the ticket is issued and also at the time the ticket is used. The most direct routing must be taken.
15.13. Rewards are based on round trip travel between origin and destination using the most direct route possible. Rewards may be for more than one flight sector. On no more than one occasion per Reward may a flight sector commence at a different point from the end of the preceding flight sector. It is possible to combine flights on British Airways and Service Partner airlines to make a round trip journey of up to a maximum of 8 sectors.

The team making the booking should be aware of this and reject any requests which fall outside it, but if not the "safety net" is the Fares dept to reject it. As above, some "creative" routes have slipped through however for the OP's example it was stopping in 3 separate places so couldn't be considered the most direct route between origin and destination, which is why we rejected the request to add a fare.

I hope that helps clarify it somewhat for you.

best wishes