I assume you mean specific insights on firms - e.g. "Bain's focus on Private Equity, especially in London, is very attractive for me". In this case, there is nothing wrong with giving these are reasons - if anything, I would encourage you to use these insights as they (hopefully) should be non-generic and can show that you really did your research and thought about the question "Why Consultancy X?"
However, I would advise you not to say "from an expert on preplounge". Rather, say that you spoke to some "current/former employees".
Hope that helps!