Hello all. My first time on this thread

I'm qualified to BSL stage 2 and I've had some experience working with sign in my past but for my own reasons (logical to me) I chose not to teach DS much sign.
I have shown him signs for toilet, food, drink. He uses toilet and food, has never signed drink, has developed a home sign for fruit and teething gel.
I have taught/encouraged the hand motions which go with nursery rhymes more than true signs (so he can join in with toddler group songs) although some are the same or similar anyway...so he has a few others but they aren't needed in everyday communication.
I'm finding recently he is signing food when he wants the toilet. He's also signing food to ask for his art materials to do painting or colouring. It's kind of pointless because to get art materials he just gets my attention and points to the cupboard where they are kept, and then I show him the various types and he picks the box he wants (paint sticks or wax crayons etc). Is this something you've experienced with your own LOs that they sign anything just to communicate that they want something?
It isn't because he doesn't know the signs, for example he never signs food when we are in the bathroom he just signs toilet, so he does know it.