Question about a claim against me from an accident 2 years ago.

Oct 2022 I rear ended a Car.
I didn’t argue.
It was very minor.
My license plate frame didn’t even crack.
She screeched to a halt in front of me to turn into a Starbucks.
Whatever. I still ran into the other car.
I gave a statement to my insurance company and didn’t hear anything about it until end of last week.
My insurance company called me and said they needed me and my wife to sign documents saying I didn’t have any other umbrella insurance at the time.
Which I didn’t.
The are also asking for insurance information for my wife’s job.
Why is this being asked.
My insurance company agent sounded very casual about it.
He said this kind of thing happens all the time.
He wants me to sign these documents so that he can disclose this information to the other drivers company.
And that they want to just pay out my maximum to avoid me being sued.
But the other drivers insurance company had a list of charges much more than my maximum coverage.
Can someone explain this?
I can send more information or wording if needed.

Edit.
This happened in Southern California.
I had full coverage if I recall correctly, but it was the minimum.
Which I think covers $15,000