Great exception!
But it works only with Table, not with CustomTable, and some extensions (FilteringTable, for example) can;t be exportable without hacks.
Could you provide opportunity to export CustomTables too?
Since the 1.5.1.2 release it should work with filtering table. There’s a discussion of this on the forum - https://vaadin.com/forum/-/message_boards/view_message/579716. If it doesn’t work please post the specifics of the issue on the forum.