Who are "They" the school or ECI?
OT is about motor, senosry, and perceptual skills and function. Just that your child has an articulation disorder means that they have had some misfire in understanding what to do with thier body to develop typically. Children do not need to have some major diagnosis to get benefit from intervention, and if you are dealing with a school based evaluation, they are not there to make a diganosis anyway. Diagnostics are private matters, sought out through evaluation with qualified doctors and therapists.
Why was you child evaluated in the first place?
If any state agency (meaning you are not paying for this) recomended a service to you for your child, take it. It is the least your child needs, because that is all the state is required to give you. School and ECI services are there to make your child functional in the school setting.
Your goals, as a parent, should always be to maximize your child's development so that they have meaninful choices in thier lives that are not limited by disablities. The specifics of need, related to OT, would be dicated by your child's evaluation data. Unfortunately, state services will never be fully in line with your goals as a parent, no matter what the evaluation data says. Ask your therapists why they think your child needs OT, and if there is any posiblity that there is a diagnosis to be had, get a private evaluation, own it, and supplement all the state services you recieve with private services that bring your child beyond functional, to maxium potential.
Make sure that you are right before you reject assistance. Many high functioning children have significant issues that need theraputic serivices. The sooner you get them, the better off your child will be. Find out exactly why before you blow this off.
M.