These institutions follow many stocks and usually have strong internal procedures and discipline. My guess is that they might for instance have various levels of monitoring to determine which stock must be checked regularly, which one is barely on their radar, which one needs high level committees to decide on significant investment... A possibility would be that they buy a few shares of a potential future investment so the stock is visible in their tools as something they're interested in, but they do not want to commit yet to any meaningful investment...

Or it might be something else entirely