Ahh...yes. Different departments word things differently. My county's SALT department says 'Not to be used for Statutory Assessments - contact department in case of query' or something similar.
In other words, they don't want their general reports being used for official diagnostic purposes, and I can kind of see why:
Say they are seeing a child every month. On month one, they comment on attention skills in the main, with plans to focus on expressive language next time. Next time, their report mainly focuses on expressive language, with some reference to the other areas also.
If one of those reports was taken for SA, then they'd have a view from SALT, but not an overall assessment.
So in short, I think it's to protect the child and the department from having incomplete reports (in terms of overview, rather than inaccuracy) used to form a judgement from that professional.
There is absolutely nothing to stop you using any of those reports to justify SA, at all. Once they've decided to assess, they'll ask SALT for a formal report, anyway.
Thinking back, we were given quite vague SALT reports and not much to go on in terms of prognosis. The actual SA report diagnosed 'severe' speech and language delays. Pity the SALT hadn't mentioned that at the time....