Five year old- Development Delay

My son has been through our local child find, psychologist and SLP.
Was told he has developmentally delay and sensory integration disorder( not a diagnosis)
Psychologist reports- As of right now they say that he has characteristics of ASD as well as significant problems with adaptive behavior and physical self care.  Stating that profiles like his are typical among individuals who have foind to have developmental delays.

SLP- Speech fluency and vocal characteristics both were observed to be developmentally appropriate.

One thing the SLP had down that I didn't understand was the following; (her words on report) It was observed, however, that his(will not name my son) speech intelligibility at the level of conversation was less than 75% in known and unknown contexts based on SLP observation. What does this mean?

Also is this heading towards a diagnosis in Autism related disorders? Thank you for your time and help.

[AUSTIN431]

my daughter was given they same diagnosis of a developmental delay and S.I.D and later autism it means that even though your son may have a good vocabulary does he know how to use the word right can he understand a word by how it was used in a conversation and can he then use the word correctly in a sentence himself can he remember the word and use it correctly again how well he can follow a conversation and respond correctly and how well he can be understood when he is speaking they look for things like does he talk to you or just babble,does he use sentences,like if he wants something to drink does he say drink or can i have a drink, does he just label things or does he understand what it is and how to use it like shoes does he understand that shoes go on your feet and that you put them on when you get dressed or does he just know that they are shoes