It is a bug that some <egXML> elements inherit the overall language of that version of the Guidelines when indeed they are not in that language. The example raised was that there may be some examples in Middle English (enm) or Anglo-Saxon (ang) (and possibly Latin (lat)) which do not have the right @xml:lang attribute.
It is suggested in another feature request that @xml:lang (and @xml:id) be applied to all egXML and exemplum elements whether it duplicates their inheritance or not.
We will attempt to create a more detailed list of egXML elements with missing/incorrect @xml:lang attributes. For the /en/ version of the guidelines it is assumed that all examples are in Modern English unless otherwise stated. So this list must look at all examples where language isn't specified and double-check that they are indeed in Modern English. Other divisions such as 'Early Modern English' will be ignored and counted as Modern English since I do not believe it has an ISO language code of its own.
We'll add the results of our investigations to this ticket.