OK, it's not just RESEARCH, but "RESEARCHability" of the source content [in this case code], and also critical analysis ability [not saying you are deficient in anything, speaking in general terms].

In this example, if the 25 files are organized nicely, and I had I nice IDE that listed class/namespace members of each file neatly, I might take 30 minutes to understand the overall structure.

Morever, If I critically analyzed this, I would ask "how many times does this event of summarizing 25 files happen"? I mean, are we changing codebases every day? No, it's a one time cost. Moreover, manually going through will provide insight not returned by LLM.

Obviously, every case is different, and perhaps you do need to RESEARCH new codebases often, I dunno!