I'm gonna give you an analogy.
Conversations are like meals. Speech is like a kitchen, cooking skills are like communication skills and words are like ingredients. Autistic people often know the meal they want, know how the kitchen equipment itself works, and understand the ingredients, but lack the cooking skills.
Most normal people have a basic pan and a basic hob, and some dried Tesco value pasta and a jar of sauce. Autistic people have a fully equipped kitchen and Waitrose meat and posh ingredients. Unfortunately, the non-autistic person will often create the better meal because they have more cooking skills and can get the most out of their kitchen, while the autistic person will spend ages getting the oven at the right temperature, not realising they've let the stuff on the hob burn.
This is the frustration many of us face. Trial and error will get us to that Michelin star, but it'll be a long slog, and mastering pasta in one particular kitchen doesn't automatically mean they could master curry in another without having to repeat the same learning process.
The reason I've given a seemingly long-winded analogy is because it allows me to take difficult-to-understand concepts and our them in terms "normal" people will easily understand. As a parent of an autistic kid, you should try this as it will help you explain your boy to others. It's not your fault other people lack the patience, ability or experience to understand autism, but unfortunately you'll have to do the work for them. Such is life. You may so find explaining the poo situation to your son by using a SIMPLE, BASIC analogy based on his interests, may be the best way if getting through to him.
I ask about dad because parents on different pages are a common factor and this makes things harder. If both understand, they will support eachother. If one does and one doesn't, the marriage will be strained. It happened to my parents. If there is another bloke on the scene, make sure he is up to the challenge. If he isn't, then this can lead to disaster. If he is, then this can often be the best situation because while he will have understanding and tolerance, he will also have objectivity and a certain amount of detachment, allowing him to be the "bad cop" when necessary. As a biological parent, it's not always easy to take sentimentality and emotion out of difficult decisions and actions, even when the decisions are in the kid's best interests. (I have a step-son with his own challenges as well as my own son and know all about this!)
I tend to say that "Autistic people don't look autistic in a photo, but will look autistic on video". That's because there's no physical autistic trait in terms of a third eye or a tail or whatever, but if you know what your looking for, seeing behaviour and interaction as a complete package will possibly give it away. Even then, it's not a given and it's always harder to detect in women.
As for growing out of stuff, you learn ways of making things work and of coping, but it's not something you grow out of. In fact, the older you get and the more crap life throws at you, the more pronounced the differences between you and "normal" people the same age will seem. Don't listen to the armchair experts, and even some professionals who work with autism are dodgey in terms of their actual ability to understand. To use another analogy: my wife's prenatal consultant was extremely qualified, but he still won't ever knowwgat it's like to be pregnant...