Thank you so much for all of the warm and supportive comments yesterday. R seems to feel much better after restarting his antibiotics. It is amazing how fast antibiotics turn around a dog's UTI. R will have tests this week so we can find out what caused a second infection so soon.
And, he's back to playing with his little brother. It seems as if our dogs have been playing for many hours every day. To check whether R wants to continue to play, I sometimes coral Hachi and take him away from R. R almost always follows us, trying to engage Hachi to play some more. That's my answer - R actively wants to play. He's not unwillingly badgered into it by Hachi.
I absolutely adore seeing R's play face and also seeing how Hachi knows that it's not serious.
Getting ready for his final move (and keeping his one eye on Hachi)...
And he roared, blowing Hachi's ears back!