MemPalace's benchmark claims have been picked apart and debunked in the project's GitHub issues:

github.com/milla-jovovich/mempalace/issues/27 github.com/milla-jovovich/mempalace/issues/29 github.com/milla-jovovich/mempalace/issues/39 github.com/milla-jovovich/mempalace/issues/125 github.com/milla-jovovich/mempalace/issues/242

(and others)

TL;DR: When independent third parties ran actual end-to-end QA instead of retrieval metrics, the scores dropped dramatically.