He clearly didn't "die" in ROTJ, at least on screen. Even when eaten, you are still alive while being digested, something Jabba even mentions. So he would have been ALIVE in the digestive track of the Sarlacc at least for period of days, leaving his fate up to debate.
Sure, the implication is that he died in ROTJ, but he wasn't an especially important character at the time they made ROTJ, so there wasn't any need to revisit it or overly explain that he was 100% dead. And him having survived by shooting his way out of the sarlacc doesn't greatly affect any major story lines throughout Star Wars lore.
You will to explain to me how Andor has even remotely retconned Star Wars.