Spreadsheet comments in xmlformat cause exception

I've ran into a strange issue while working with comments in excel spreadsheets. When not using xmlformat (.xls) comments work fine, but if I start using xmlformat (.xlsx) I start getting "Multiple cell comments in one cell are not allowed".  I'm running ColdFusion 2016

I'm including a snippet of code below that will work fine for .xls style documents but error out for .xlsx style documents.

<cfscript>   // Runs without error   mydoc = spreadsheetNew("Test", false);   setComments(mydoc);   spreadsheetwrite(mydoc, "#expandPath("./")#test.xls",true);   writeoutput('<a href="./test.xls">Download good</a><br>');   //Throws java.lang.IllegalArgumentException: Multiple cell comments in one cell are not allowed, cell: E9   mydoc2 = spreadsheetNew("Test", true);   setComments(mydoc2);   spreadsheetwrite(mydoc2, "#expandPath("./")#test.xls",true);   writeoutput('<a href="./test2.xlsx">Download bad</a>');     //write some data and comments to the spreadsheet   function setComments(doc){     for(row = 1; row <= 50; row += 1){       for(col = 1; col <= 50; col += 1){         spreadsheetSetCellValue(doc, "row: #row#, col: #col#", row, col);         SpreadsheetSetCellComment(doc,{comment:"(#row#,#col#)"},row, col);       }     }   } </cfscript>

Is there some difference in using .xlsx that I don't know about, or is this a bug within ColdFusion?

Thanks,

Chris