findbugs suggests static inner classes for converters

Findbug gives the following message for all converters used in ApplicationConversionServiceFactoryBean_Roo_ConversionService:

[INFO] The class com.myproject.toplevel.web.ApplicationConversionServiceFactoryBean$ApplicationConversionServiceFactoryBean_Roo_ConversionService$7 could be refactored into a named _static_ inner class 

Is there a specific reason the approach was kept as not static nested classes? Could there be an improvement for this?