This right here says (2) fixtures / 13" center spacing. That means, to get the aforementioned "spread," they are placing
TWO fixtures 13" apart. Yes the spread on paper looks good, perhaps better than T5, because they are using two fixtures close together. The fixtures you show in the picture above are more than 13" apart. Therefore, the spread won't be the same as the chart you posted. You say the XR-15's above cover 24"x 24", and they would probably cover 36" x 36", or even your whole bedroom for that matter if you mount them on the ceiling. But if you mount them over the tank as shown above, your PAR won't match what is indicated on the color chart.
Also notice that at the bottom of that picture, they state that the measurements are taken using TWO lights mounted 12" high over a 120G tank but they don't mention the dimensions of the tank. What size is the tank you show the above ones mounted over? Running the numbers myself, that tank looks to be 40" long. A 48" tank would be stretching it at the outer edges.