PS...rereading the link...the drought was before 75,000 years...while you say the volcanic eruption was 74,000 years ago...but it is not too likely that they have a real precise age on the drought...unless they have a volcanic ash layer to date (there is a young volcanic center just north of Lake Malawi...).
You link to an abstract....should be considered different than a scientific paper, which would have a lot more detail.....I think this unconformity in lake Malawi has been known for at least a few years...maybe a decade or more...
Chris