In a word Joe Yes.

I too began by playing things I did not understand- they often sounded fine but I could not transpose them, or use them in different settings.

One of the things I am trying to achieve at present is the ability to sight read any chord in any key.
In order to do this I ONLY play notes I understand. By understand, I mean something different to the ordinary use of the word, I mean understand musically.

An example:

To 'understand' the concept of a triad

1] Know the intervals involved in terms of names, steps, know the minor, major, diminished and augmented forms.
2] Know how to play these notes in their inversions instantly in any key, in any pattern. This involves muscle memory and the use of different fingers (according to where you come from and where you are going finger placement wise). It involves many different ways of the fingers transversing the keyboard - all this muscle memory must be automatic
3] To know aurally - that is to play a note because one can hear it.

Knowing in this sense is both intellectual and muscle memory. It is a great deal of work (!)
When this is achieved then there is freedom - emotional freedom.

Of course it is possible to achieve all this without learning to read music, but it's the long way to go. It's about mental categorisation and planning.

My first piano piece was a Minuet by Bach. I learnt this piece 'off by heart'. What I noticed was that even though this piece exposed me to muscle memory runs, these runs were not appearing in my improvisation. I figured out there were two reasons. Firstly, I did not know the relationship between the run and the chord, and secondly I was not thinking of this relationship quickly enough to implement it.


Z

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