One valid use case for solutions like this is if users are allowed to run their queries inside a database or api. I'm often in the situation where you try to a

One valid use case for solutions like this is if users are allowed to run their queries inside a database or api. I'm often in the situation where you try to add all kinds of parameters to a query-field in the UI but no matter how hard you try there will always be a power user with the request to do some combination of AND/OR/CONTAINS/NOT with nested parenthesis that is not supported. After hundred such requests you get sick of it and just want to expose the raw DB-query to the front end, which obviously is a bad idea for security reasons. Having a safe intermediate representation that is sophisticated enough for some logic can be a good idea. Instead of reinventing your own, using this language can be done, as long as it has a mapping into each database query language.