Correct, the tag history binding always adds the t_stamp as the first column. I see what you are trying to do. In this case you have to make a new dataset in scripting since you can't remove the t_stamp column. Do the following:
1) Add a custom property to the root container called origData that is a dataset. Right click and select Customizers > Custom Properties.
2) Bind it to the tag history binding you have right now
3) Right click on the root container and select Event Handlers...
4) Choose the propertyChange event and use code like this:
if event.propertyName == "origData":
origData = system.dataset.toPyDataSet(event.newValue)
newData = 
for row in origData:
event.source.getComponent("Chart").Data = system.dataset.toDataSet(["Col 1 Name", "Col 2 Name"], newData)
Let us know if you have any questions.