Hm, that should throw an error (but I see that it doesn't).
The uitable should be a child of a "Figure object (default) | Panel object | Tab object | ButtonGroup object | GridLayout object" (parent info). You're setting it as a child of a uiaxes. You probably intended to set it has a child of the figure.
uitable(app.UIFigure,'Data',tdata)
% where app.UIFigure is your figure handle
However, if you're using app designer, the table should typically be created from within app designer and should already exist before you populate it with data. In that case,
app.UITable.Data = tdata
% where app.UITable is a handle to an existing uitable
