Octave: Unable to pass optional arguments into VBA function (when adding excel sheets via COM server)

I'm attempting to add sheets to an excel file.

It should be fairly straightforward; however, the following minimal working example below fails when attempting to skip optional arguments using empty braces. (Is this not correct? Source 1 Source 2)

clc
clear

% if COM error occurs, excel process remains open.
% use task manager to end process, else 'a.xlsx' file remains "in use".

srvr = actxserver('excel.application');
wbks = srvr.workbooks;

pth  = fullfile(pwd, 'a.xlsx');

if ~exist(pth, 'file')

  wbk = wbks.add;
  wbk.activate;
  wbk.saveAs( pth );
  wbk.close;

end

wbk = wbks.open( pth, 0, false );
wbk.activate;

wshts    = wbk.worksheets;

shts     = wbk.sheets;

wsht     = wshts.item(1);
wsht.activate;

sht      = shts.item(1);

wsht.select(true);
sht.select(true);

%{
https://docs.microsoft.com/en-us/office/vba/api/excel.sheets.add
https://docs.microsoft.com/en-us/office/vba/api/excel.worksheets.add
%}

shts.add(sht);     % functions
shts.add(wsht);    % functions

shts.add([],sht);  % fails
shts.add([],wsht); % fails


shts.count

wbk.save;

srvr.quit;

Here is the error:

error: com_invoke: property/method invocation on the COM object failed with error `0x800a03ec' - Z
error: called from
    trash at line 46 column 1

Note that the add functions until skipping the first input. Are square brackets the wrong method to skip an input?

Original source.

I have also posted this in Octave forum.