Their system watches for incongruent itineraries over the course of weeks.

Your situation is a bit of a corner case though. I still don’t believe their system will block you. But those stories you’re reading online are from ppl who booked several flights three or four weeks+ out and the system catches it and cancels one of the tickets.

My suggestion though is to let southwest fix it rather than be proactive. If their flight ends up canceling southwest will auto book them onto the next available flight and update their ticket for free.

Southwest is notorious for holding flights until the last passenger arrives. Flight out of Oakland may be delayed because it’s the last flight of the night and an incoming flight with a layover passenger has been delayed from earlier in the day. The plane will eventually leave, but everyone shares in the delay.

I usually book morning flights on southwest for this reason. The last flights of the day have the highest chance of delays. Because the cascade effect of delays during the day.