I think the method you are looking for is the axisBetweenCategories.
I tried this method and it doesn't appear to be the correct one. I've tried both axisBetweenCategories(true) and axisBetweenCategories(false).
Maybe you can post a sample showing it not working and an image of what you are trying to get? This is from the other post where I included a link to a jsfiddle:
And this is if I change that method to false:
I don't know which "other" post you are referring to. However, the previous reply mentioned using the axisBetweenCategories(true) method. Since I wanted to modify the way the categories were displayed, I used chart.axisCollection($.ig.excel.AxisType.category).axisBetweenCategories(true). But to get it to work you used chart.axisCollection($.ig.excel.AxisType.value).axisBetweenCategories(true), which is not at all intuitive. In fact, after the spreadsheet is generated in the jsfiddle code you mention above, if you hover over the vertical axis, the description is "Vertical (Category) Axis", which is the one that got modified by the chart.axisCollection($.ig.excel.AxisType.value).axisBetweenCategories(true) statement. That doesn't seem right, but it works.
I assume Infragistics must always consider the vertical axis the 'value' axis, even when rendering a Bar chart, where it is treated as the 'category' axis.
I was referring to the fiddle I had included in a reply to your post about creating a single value series. The pt is valid about category/value axis type and I'm not sure why the indexer is this way so I forwarded that question to someone who worked on that part.