I am not a controller but if he had said unable he would have been doing a 360 to the right.
If the Cessna was parallel to 101 it would have been on a course of about 175 deg true; United was climbing on course 298 deg. How close can the Cessna be to the 777s track and still have room to start a right 360 without making things worse?
If you've ever flown that route, you'd know that everyone had plenty of time to react and comply with instructions.
To know that we have to know just where the Cessna was at a given time in the transcript. If I fly the route once or twice I will suddenly be able to intuit that? To what accuracy?
I finally looked at the map. It turns out Hwy 101 crosses the runway extended centerline 3900 ft from the departure end of 28L; FWIW, the terrain reaches 650 ft or so 3.7 nm from the end of the runway.