After the initial report was published a number of let's say "conspiracy theorists" made their own articles and tried to find new things sometimes with doubtful methods.
The original research doesn't claim that any particular piece of argument in itself is conclusive but that combined together, it creates a corpus of oddities that amount to a strong doubt.
> Meanwhile Jeanne was apparently able to name old professors and maids of hers, things that her daughter would probably not have known or remembered.
In particular she made several "mistakes" when relating the names of people living with them, including the maid as you mention, which would be consistent with a maid that accompanied Yvonne to school but not Jeanne. See "Whom did Marthe Fousson accompany to school?" from the link above. Similarly for the piano teacher.