Because there is a disclaimer, you are disregarding a thoroughly tested product that solves your exact problem? One which is released by one of the premier MySQL consultancies with the author of "the" MySQL book as the designer?
You could make the same exact disclaimer about SQL statement and it would be true:
"INSERT modifies data and structures. You should be careful with it, and test it before using it in production. You should also ensure that you have recoverable backups before using this tool."
"ALTER modifies data and structures. You should be careful with it, and test it before using it in production. You should also ensure that you have recoverable backups before using this tool."
It's just good advice to test stuff before you use it in production. Discarding an awesome product simply because the authors (responsibly) mention that you should probably test it out seems overly paranoid and would severely limit your choices. Percona Toolkit is the most well known and reliable set of tools out there in the MySQL ecosystem.
