I noticed on these drawings: that the living room balcony subsequently was reduced in size, particularly on the right hand side,
the entry wall appears to have had some vertical batten. I imagine they would have provided nice glimpses of the river and some decent light. Im also guessing that Mr Wright decided he didn't want any views out of the entry and wanted it reasonably dark, thus eliminated any view entirely.
This model shows just perfs at the top of the entry walls!
It also shows interesting buttressing to the bedroom balcony sub flooring and a brickwall at the end of the Loggia which I realise I can actually see on this alarmy photo!
but as far as I can tell - there is no buttressing indicated on the drawings seen so far -only some sort of ventilation slots.
Buttresses, I guess were added for lateral stability of such a long wing.