I had to have my bone scan run a second time (same day) because they spotted all the broken bone healings I had as a kid on the first run. I had mentioned that on the info sheet, but I guess they didn't take it seriously until my legs lit up like Christmas trees.
As already said by others - with a lower (say <20?) PSA, the bone scan is more a doctor's lawsuit preventer than anything. I was happy that mine was effectively clean, which gave me a baseline for any future tests, and bought me a few days of "its not as bad as it could be". (My PSA was 7.4 at age 56 diagnosis)
The bone scan added a lot more anxiety to my life than any PSA has (yet), and for no good reason.
On the Gleason scores, you should see them as G x+y = z. That is the best way to relay them to us, as the order is very significant. Mine was a G 4+5 post op. A G 5+4 gives the same sum, but is significantly worse.