And even then, the “IV” was meant to evoke the feeling of being dropped into an ongoing narrative, as opposed to actually being part of one. Lucas hadn’t actually set anything in stone. In 1978, he was still going with the idea that Vader wasn’t Luke’s father. That reveal in Empire Strikes Back is the most influential movie retcon of all time.
And even then, the “IV” was meant to evoke the feeling of being dropped into an ongoing narrative, as opposed to actually being part of one. Lucas hadn’t actually set anything in stone. In 1978, he was still going with the idea that Vader wasn’t Luke’s father. That reveal in Empire Strikes Back is the most influential movie retcon of all time.