Los Angeles - San Diego - San Francisco

In February this year, exactly like February last year, and almost the same trip, the same strange incident happened. I picked up the car with a full tank and returned it with a full tank, but both times I got charged $65. I only found out about it after returning to my home country last year and multiple complaints led nowhere. This year I made sure to point it out when returning the car, and without asking any questions, they refunded me immediately! I can't help but suspect this might be intentional. I hope for an explanation. ALEMO is usually cheaper on the ZUZUCHE platform, but once you get there, they strongly recommend upgrading the vehicle and adding extra insurance. Various charges (like $145 for 8 days of GPS; last year, I got talked into adding over $700 of extra insurance and received a free GPS, the charges can be very arbitrary), and then casually being charged $65 for 8 days of rental at $15 per day, once confirmed, they would immediately refund it! Am I being overly suspicious?