It’s a complicated matter which makes it super dificult to make it easily understandable for people without a degree in the topic. I am studying immunology and have my issues understanding it completely. What I can tell you though is that the effectiveness of HIV medication is very unlikely related to the inserts identified by the researchers. Why am I so certain of that? The HIV medications are protease inhibitors, so substances that block a specific enzyme of the virus. The inserts that are alleged to come from HIV are in the spike proteins (part of the virus surface) and these proteins are not the target of the medication. The sequence of the nCoV protease doesn’t seem to contain any insertions. The escaped bioweapons / failed experiment theory is certainly the more exciting one and I can understand why people would want to belive it, but I think for now this is not really convincing evidence. The overlapping sequences are very short, these kinds of sequences are not completely random but tend to follow certain patterns, the inserts don’t seem to transfer any of the unique properties of HIV (especially the ability to infect T-Cells via the CD4 surface protein).