I think the intended use of the excursionist perk is e.g.
Round-trip (open jaw) USA-Europe:
SFO-FRA-LHR (stay in London for 2 weeks)
LHR-FRA-TXL (stay in Berlin for 2 weeks) <--- free flight
TXL-EWR-SFO
The way they worded it / coded it in the ticketing system may allow more creative uses, but if you think of this as the intended use you will see why they call it a perk. It basically gets you one free flight in your destination region, which is extremely convenient when paired with overland travel or an open jaw ticket.
Personally I preferred the free stopover pre-Oct2016 perk, but this is how it works now and it's probably more clear to casual users.