Excel supports deselecting cells from selected ranges, e.g. selecting a range from cell A1 to A10 results in a range A1:A10. Then deselecting cell A5 from that range produces two new ranges - A1:A4 and A6:A10.
Now a more complex example - selecting multiple ranges with intersecting cells - A1:B10, A5:D10, A9:C14 and A9:G9.
Deselecting cell B9 in Excel produces a new range with cell A9 only and then a range C9:G9. And B9 should be excluded from the other 3 ranges.
Currently the Spreadsheet widget does not know how to do this. There is no logic to decide what new ranges should be created on such operation. What it currently knows is creating new ranges and these ranges may overlap. Thus clicking on cell B9 creates a new range with cell B9, instead of deselecting B9 from the already selected ranges.