Steph_D... I wouldn't worry too much about this.... it is a trend these dsays to give these types of kids a label... and sometimes that helps to understand them better and sometimes it focuses on their difficulties too much and magnifies the situation...
In the past all these kids were called shy... and being shy was a normal part of being a child... and it still is... but we call it different things.
Me... I never spoke until I was over three years old... not one sound... not even 'da da' or 'ma ma'... I never spoke in infant school and almost never in Junior school... and mostly I played on my own. I was called 'quiet' or 'shy' or even 'introverted'... but asperger syndrome, dispraxia and selective mutism etc... simply hadn't been invented and actually wouldn't fit me as an adult cos now I talk too much. I didn't talk because I didn't want to... I didn't see the need... and I didn't want to talk until I had something worth saying... and I wish my mum had lived long enough for me to have been able to explain that to here cos I know she had been quite worried. I think thst were I a kid now I would have been given some syndrome to tie my flag to.
Now with all children we praise what they can do and enjoy their company and play with them and do activities with them and encourage all aspects of their lives.... and we see the aspects of life they don't thrive so much in and look at different ways these areas can be developed in them... to try to make these 'blocks' they might have less dauntinhg and more managable to them.... and this is why we now give these labels...simply to make it easier for those working with our children identify more easily these areas which need more support.
My daughter is a touch autistic and professional intervention over the years has given us a lot of stress and worry... but we all pushed through and now my child sometimes talks to me and is more relaxed... and I wonder why the professionals didn't leave well alone and just wait patiently for her to flower...
... sorry I can't be of more help... God bless.