This appears to have nothing to do with data linking.
Your first plot sequence starts by manipulating the axes grid setting. That does not affect which graphics objects are present. You then hold on, which says that all new graphics objects are to be added to the ones already present in the axes. You plot some things and turn hold off. Next loop cycle, you change grid settings which does not affect the graphics objects, then you turn hold on, the new plot calls add to the previous ones for the axes, and so on.
The second axes though, never has hold on in effect, so the plot() call erases the current axes content each time that plot() call is reached.
hold on only applies to the current axes, not to all axes.
