For each block that is used by the course, MyMoodle will call a print_overview function, if the block has one, similar to the call to a module's print_overview function, in order to generate a similar activity message. This is something we support with our custom-built blocks on our site and which is not supported, at present by many core blocks. However, we feel that it may be worth considering modifying some of the core blocks to do this in future.