K.P.
At his age, play skills are fairly well-defined. There is a developmental continuum of "play skills" which start very rote, as in bangning things on the stroller to see what noise it makes and become increasingly abstract and complex from there.
By the age of 2, most children are able to use multiple objects to engage in short, but focused play schemes. For example, a two year old should be well-versed in pretending to "do things" with "real things"... feed a doll with a bottle. Over the next year or so, that play becomes more complex... feed the doll, "burp" the doll and put the doll to sleep. This is known as "linking schemes".
My guess is that your son is using "things" to engage in functional play. He'll pretend to feed himself with the bottle, but isn't yet going from "self" to "doll".
I don't know if you can Google this, but see if you can find any of the Transdisciplinary Play-based Assessment scales online. Toni Linder is brilliant and her descriptions and age ranges are really wonderful! I was trainined in her assessment model and used it to do countless EI evals in my early professional career.