I might be swinging in the wind here, but want to offer my side of things...
On paper, Bee is a train wreck. Stroke as a baby, CP, epilepsy, sensory issues, feeding challenges, diagnosed with ASD at 2, medical issues by the boatload requiring a 1:1 nurse while she is at school just to attend to her medical care and on and on... If you see her for a brief period most of the time, however, none of that is evident. The EP saw your DS for a brief period.
The other professionals who saw him longer saw evidence of different concerns, and their opinions, of course, carry merit. The EP, however, may only legally report what she observed at the time - the rest is just hearsay...
Here is a good example - when Bee started school this year, she was a month and a half late because she had been in hospital. She came in to a class that was already settled into a routine with a new teacher, new layout in the room, and a lot of personal anxieties. If she had been observed by an EP in the first few days, they would have seen a VERY distressed, self-abusive, volatile, inattentive and disruptive child who required extensive support beyond what was already in place for her at the time. Fast forward to the first couple of days this week - Bee has settled in, uses a visual schedule to transition from one activity to another, is happy and helpful, willing to work and making gains. Her sensory issues are not overwhelming and she has found her comfort in the classroom. If the EP came to see her now, she would say that she transitions well, in engaged in the tasks at hand, seems happy and social - certainly not what the scores of reports that are filed away have to say about her. Is this is a different child? No, but she is coping well in this setting (and so are the TA and the CT) without additional support beyond what the class has in place as a whole.
The EP is professionally obligated to observe, assess if warranted, and report. They are not the gatekeeper of the LA funds, and frankly would probably like to see your DS in a MS school. However, I am certain she was trying to open the door to the fact that, because your DS did have a difficult beginning to the year, but seems to have settled well now, the likelihood of him getting 1:1 support full time is not very strong. If you are that adamant that he needs 1:1 support, then she is not out of line suggesting that he might get the support you feel is appropriate in a SS setting. All of this, of course, is based on her 1 hour of observation - just a brief snapshot in time.
Statements from the CT are crucial - about incidents, about disruption, about educational time being denied to the other children in the class because of the need for excessive attention to your ds (It stings, but that is the kind of thing that the LA will pay attention to, particularly if there is standardized testing the teacher has to prepare the entire class for, kwim?)
Like I said - perhaps she got him on a good day, perhaps he is settling in exceptionally well and has found his niche after all... but don't shoot the messenger.