If you are that distrusting, then do the SHA1 conversion yourself. It isn't that complicated:

  sha1=$(echo -n 'happy123' | tr -d '\n' | openssl sha1)
  result=$(curl https://api.pwnedpasswords.com/range/${sha1:0:5} 
    2>/dev/null | grep $(echo ${sha1:5:35} | tr '[:lower:]' '[:upper:]'))
  echo "Count: ${result#*:}"

With that, I can see that the password 'happy123' has been "pwn'd" 70,617 times.