Reading the original issue (symfony/symfony#24935) I don't think we should document this explicitly. It's a nice to have feature that works exactly as a user would expect. There's no need to read docs about it to know how to use it.

@javiereguiluz IMO this should be documented explicitly because people who would like to use this feature and are googling for it (like me) not necessarily will read symfony/symfony#24935. Also that issue does not define how it should be used, author just wrote how he tried to use it (when it wasn't supported).