No - you can't enter Africa twice!

The sticky is misleading and needs a rewrite (I have posted to that thread).
"(c) a transit without stopover in Europe on a flight between Europe and GHANA/NIGERIA/KENYA/UGANDA/TANZANIA or vice versa." is just wrong. The rules say "a transit without stopover in Europe on a flight between GHANA/NIGERIA/KENYA/UGANDA/TANZANIA and another continent or vice versa." In this context "another continent" means NOT Africa or Europe.

The provision is to allow a second entry into EUROPE in order to get to the named countries. For example:
HKG-JFK-xLHR-ACC-LHR-HKG is a valid xONE4. It would not be allowed without the exception because you have two entries into Europe.