You are having a normal recovery. As you know, this is a long long Long recovery. You had both knees done together and the energy drain is very real. You have excellent ROM. Soft tissues are still quite upset and they need time to heal.
Walking around a bit and 5 minutes on your bike (at zero resistance) from time to time is good. If the bike does bother you, cut back to less minutes or less times a day.
Remember, it’s not exercising that gets our range of motion back, it’s Time:
Time to recover.
Time for pain and swelling to settle.
Time to heal.
Our range of motion is right there all
along just waiting for that to happen so it can show itself.
In the general run of things, it doesn't need to be fought for, worked hard for or worried about. It will happen. Exercise as in strength training is counter-productive and in the early weeks does more harm than good. Normal activity is the key to success.
I am going to tag
@Josephine
our forum administrator and nurse director to address your concerns.