I recommend you to learn about the SCALM technique which is also called “Structure Chunk Associate Locate Memorize”
https://forum.artofmemory.com/t/introducing-the-super-clever-advanced-learning-method-scalm/52020
A picture takes more storage space than a word and when using a memory palace to memorize a sentence I believe that many people think of an image (which takes more space than a word)and then encode a word and a word takes lesser storage space than a picture,
And I think that if a person could use his entire memory capacity when memorizing text then he will not need to use most of the memory techniques in which images are used as images use a lot of memory maybe in the range of a single kilobyte to hundreds of kilobytes for an image with a high resolution and I believe that a single word takes only a few bytes most of the time
And if that person did use The Memory Palace for memorizing text then he will waste a lot of his memory storing images instead of text as he will use his full memory capacity instead of only using the memory capacity of his Visual and Spatial Memory.