Because it is the default behaviour of streaming.You can add a prop reverse=true to StreamingChart and change the code ret.reverse();based on condition.
So basically, you are suggesting to add one additional property to the streaming chart, right? Based on its value, apply ret.reverse(). This means if reverse is true, apply ret.reverse(), otherwise don't. But it is required to reverse our data every time, otherwise, I believe the most recent data point will be at the beginning of our plot. I've tried one more approach here. If our data array is full, this graph shifting won't happen. So, if we initialize our data list with null values, there won't be any visible shift. What do you think about this solution?
I would suggest changing the behaviour in StreamingChart so that it can be used at other places. If you want to reverse it then you can still do it. I had achieved reverse direction with the following piece of code. Basically, creating an array of 75 points, filling it with available points and reverse. You can change it based on reverse=trueflag. In your case, simply reverse, not need of 75 points.
Array.from(new Array(xRange).keys()),
...(data.datasets?.map((d)=>{
let ret = [...d.data];
ret.reverse();
return ret;
})??{}),
Unrelated to this, I think instead of showing disk sizes in bytes you can show them in a human readable format like below used in Statistics tab of Tables collection node.