Apache POI only return one data validation although there are two in the sheet

Question

I have a workbook with two sheets. Sheet1 contains two cells with data validation. Cell1 has data validation with source from Sheet2 while Cell2 has source from its original sheet. When I print out the size of data validations in sheet1, it shows only 1 instead of 2.

System.out.println("data validation size: " + refSheet.getDataValidations().size());

My questions,

1. Does ApachePOI only support same sheet data validation?
2. If the answer to 1. is no, how could I overcome the issue I mentioned above?