The linked thread is about the WPF RadSpreadsheet. The Kendo UI Spreadsheet is a different component. To check whether there is a merged cell in a given range, you can use the _mergedCells private property. It can be accessed like this:
var mergedCellsInRangeArray = sheet.range("A1:G1")._sheet._mergedCells;
It is an array and its length will return 0 if there are no merged cells in the range, otherwise it will contain objects with more information on the merged cells.
See this dojo example, in which initially there is no merged cells and on pressing the button above the Spreadsheet a cell is merged, which is reflected in the _mergedCells property value.
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