This was excellent. Some clever clues and difficult but not stupidly so.
Three distinct PDMs for me - the significance of the commonality of the extra words, some thematics words and finally the thematic phrase.
I spent far too long looking for a fourth additional example as well as the completed bottom line before reading the preamble again and realising it was not there.
I have no difficulty with the use of singular thematic elements. The removed letters spell out four of them (pleural) in four separate parts of another thematic item (singular) - as in the thematic phrase.