G.♣.
This is actually extremely common, and it's great that your school has the resources to offer this. My SIL is an SLP (Speech-Language Pathologist) at a nearby district. She is the only one at her school. She works with many kids who have been tested and now have an IEP (Individualized Education Program). She does have time to work with some kindergartners who just need to work on a few sounds, but not much. She has many kids she is required to work with because of their IEP and doesn't have much time left over.
My oldest is in 4th grade and doing great. When he was in kindergarten, he was pulled out to work on some sounds. Can't remember which ones, but I do believe he worked on the "th" sound, as he often pronounced it as an "f." I don't remember him being pulled out beyond kindergarten, but I know he hasn't had speech for at least 3 years.
My youngest has been in speech through the school since he was 3. I requested that he be tested, and he has had an IEP from the start. His IEP requires that he receive a certain number of minutes each week, and outlines very specifically the areas where he struggles and what he will be working on in the short-term. We have an IEP meeting at least once a year to discuss his progress. When he was in kindergarten he had further testing and now has an IEP for other reasons as well, but even when it was just speech we had a meeting once a year.
Feel free to simply contact your son's teacher and whether or not he is still being pulled out for speech. If you feel he is making improvements, great. If you don't of if the teacher doesn't, feel free to ask for further testing. Nothing wrong with him having a speech evaluation. If it is determined he should be receiving speech services, he will receive an IEP. No reason to be alarmed. It's just a way to put in writing what it is that he needs, and it protects you. If your son has an IEP, the school is required by law to follow it. So you know he will receive the services he needs. An IEP does not have to be there forever. If he improves and no longer receives services, then he will no longer need the IEP. But this would be addressed at the IEP Meeting.
Don't be afraid to contact your son's teacher and ask these questions. If your teacher cannot give you answers about speech (and keep in mind, many cannot. It's not their area of expertise), feel free to make an appointment to meet with the speech teacher (SLP). There's no reason you shouldn't be able to meet with someone so that you can learn more about how your son is doing.
ETA - I'm not sure what an intervention team is, but when we have an IEP Meeting, it includes a team - classroom teacher, speech teacher, principal, social worker, resource teacher, I'm drawing a blank on who else has been there :-). I'm guessing that the intervention team are the individuals who specialize in various areas of special ed, would do any requested evaluation, etc. The individuals out our meetings also meet to discuss students who are having trouble to help teachers, suggest strategies for teacher who have a child who is struggling (with academics or behavior) and possibly suggest to parents that testing be done.