Word boundry not working in MySQL 8.0.16 REGEX?

Question

I am baffled...I am using MYSQL 8.0.16 and according to the manual a simple word boundry, \b, should work. But it wont work...

my query:

SELECT *
FROM  `wp_posts` 
   WHERE (post_title REGEXP '\bUSD\b' 
    )
   AND post_type = 'post'

I am using mySQL 8.0.16 and I also tested it on 8.0.18, with same results...

help appreciated

cheers

ben