I see two major issues:
(1) For the 'convalescent sera', it is essential to know which variant(s) caused the infection, as that strongly affects which variants there will be immunity to.
(2/ Differentiating double-jabbed and boosted individuals implies (incorrectly, based on the data I've seen) that a third dose is qualitatively different from a second dose. The correct way to differentiate is by the time elapsed since the _last_ dose. Whether an individual had two or three or four doses _can_ be a proxy for time since last dose, if that's the only information you have, but it isn't a very reliable one.
Both of those issues, but especially the first, reduce the value of the results and make it difficult to draw conclusions.