Different Bitcoin addresses from coinbase?

So I sold a bunch of stuff and the guy wanted to do it in increments. He said he used coinbase and only used the same wallet, but does anyone know why every time he sent, there were 2 addresses and every time it was different. Is it a coinbase thing?

I've cut out the last few digits and letters, but basically this is it

 

One probably has something to do with the fee, or some coinbase mechanism.

And yeah, they're likely generating unique addresses every time.

 

You could also send it to his wallet address continuously - that one will always accept the payments. I think it may also be related to your own wallet.