Searching Text with $regex and $text

A search for the word "reading" can return a document that does not contain "reading". The two queries below search the same six users, and the second one returns Zoë, whose description says "reads".

db.users.drop()
db.users.insertMany([
  { name: "Alice", description: "Alice loves reading and traveling." },
  { name: "Bob", description: "Bob enjoys cycling and hiking." },
  { name: "Charlie", description: "Charlie likes gaming and reading." },
  { name: "David", description: "David prefers swimming and biking." },