But Noble could play fetch forever

Morning everyone,

Could you please help me out with the following question? What's the value of the bolded "but"? I mean, shouldn't it be a ; or a "because" (as...)?
At first, Jimmy, the narrator, is happy he's not alone anymore. He's met Noble, a scruffy dog, with whom he's now playing fetch. However, he soon realizes he'd love to be alone as the dog may play endlessly. The extract has been taken from "The Valley of Lost Secrets" by Lesley Parr. Thank you.

it’s good to have someone to play with, even if it’s just a scruffy old dog. [...]
A million throws later I think I’d rather be on my own but Noble could play fetch forever. And if I try to move away, he follows me, leaping and barking like mad.

Good morning. But contrasts Jimmy's attitude with Noble's attitude. Jimmy is tired of the game, but Noble wants to continue. This is an ordinary use of but. Here is a similar example: I wanted to stay at the resort for three more days, but my wife was ready to go home.