What's the issue? Even IF it only had the one oil change in that time frame, it's at most 4k overdue.
Use that as a negotiating tool if you like this car. That time frame I seriously doubt there will be any issues.
If you're REALLY concerned about it, have them do a Blackstone oil analysis on it for you. Cost is $25 I think.
It's not the dealer that says it, it's Toyota. I think the engineers that Toyota hires know what they're doing.
Also, there are no stipulations in a lease in regards to maintenance, you get it free for 2/3 of the lease if you stick to ToyotaCare and get a 12k per year lease, but there is nothing in my contract that said I had to do maintenance anywhere in particular, or at all.
You own the car in a lease just as much as you own it if you finance....