Great explanation and background, thanks!
My answer would be, based on extensive experience of many amps of different genres, yes, as an amp can improve all the other parameters of sound quality, the lyrics would become more intelligible. I would not agree that it would happen in isolation from other characteristics that change along with switching an amp, but it is a part of the outcome of an amp having greater/lesser resolution, headroom, etc. :)
My answer would be, based on extensive experience of many amps of different genres, yes, as an amp can improve all the other parameters of sound quality, the lyrics would become more intelligible. I would not agree that it would happen in isolation from other characteristics that change along with switching an amp, but it is a part of the outcome of an amp having greater/lesser resolution, headroom, etc. :)