Our paed was the same about SPD AndiE. That was frustrating, because I was more interested in the SPD diagnosis than the ADHD. I wanted that under control - at least to try get that under control - before we went further with the ADHD diagnosis.
No matter what we did for her SPD though. nothing was working for the lack of concentration & I had to go the other way

When I was first referred to the OT with DD, we were under an EPC Plan - 5 sessions. The initial assessment cost about $250. I don't think that was covered by the EPC though :/ After that I paid the amount minus the EPC, then received money back from medicare. In total I was out of pocket about $20 for each session from memory.

Once there is a diagnosis you can get the Mental Health Care Plan. Pretty sure its 12 sessions a year under the MHCP. My GP was able to give me those, but still only after I had paed diagnosis.