XSD files not supported anymore

A few weeks ago I was testing a feature for transforming PDF files of different types into a standardized XML document based on a XSD schema. But recently I get the error that the XSD file format is not supported (and in fact it is not in the official list). But I do not understand why that, it worked before and it was really useful. Why isn’t such an important format like also Json schema files supported anymore ? XML yes, XSD not… confusing