Clarify the not-Java-packages guidance a bit.

PiperOrigin-RevId: 914412431

Author: protobuf-github-bot

content/programming-guides/style.md

@@ -96,8 +96,10 @@ Package names should attempt to be a short but unique name based on the project
 name. The package should not be coupled with the directory path, especially when
 the files are in a deeply nested path.
 
-Package names should not be Java packages (`com.company.x.y`); instead use `x.y`
-as the package and use the `java_package` option.
+Package names should not be Java style packages, even when located in Java or
+Kotlin directory. Do not use any of `com.company.x.y`, `com_company_x_y`, or
+`java_com_company_x_y`. Instead use `x.y` as the package and set `java_package =
+"com.company.x.y"`.
 
 ## Message Names {#message-names}