Being exposed isn't about how many people are in front of you. It's about the specific drill form. You'll notice that the tubas are right up front for Crown's ballad too (sitting down, playing with one hand, I might add). The Bluecoats play in a lot of so called "power forms," with the brass reasonably close to each other.
Crown's show:
Opening Mahler segment, Bb minor - spread literally endzone to endzone, coordinating 16th and 32nd notes with no pulse from the drumline (while doing body).
First Mahler impact - STILL spread endzone to endzone. Tuba actually winds up on the 50. Descending quarter note triplets beginning on high F, culminating in low C resolving to Bb minor.
Triplet runs - hornline spread out (30 to 30 I believe) with no drumline pulse. Tuba runs beginning on E in the staff, descending triplets at 192 bpm.
Next Khachaturian impact - virtually crown's only "power set."
End of Khachaturian - hornline spread out to the side 2 15 yard line. Tubas jazz running right up front.
Danzon No. 2 - tubas begin far away from the front and behind the drumline, leaving no audible pulse.
Danzon impact - again, hornline spread 25 to 25. Tubas walk an amazing tango bass line spanning an octave and a fourth, from A below the staff to middle D. Again, more body.
Nimrod - the most exposed moment in dci this season. A capella brass. Tuba right up front, brass judge there every time, sitting and playing with one hand. Bass line again spans an octave and a fourth, from low C to high F.
Nimrod impact - tubas kneeling right up front.
Nimrod, last chord - hornline spread endzone to endzone, front sideline to back sideline, in a hugely exposed X, giving judges the chance to sample any player they want.
Mahler reprise - tubas playing a segment of the Mahler bass line, feet in double time, taking large strides as far out as the 15.
Reprise impact - company front spanning 10 to 10. Tubas far away from drumline pulse. After the company front, the tubas jazz run at 208 bpm playing high Fs, coming in for sixteenth note pickups with no pulse.
Promise of Living - another company front, tubas streched from 45 to 5. Mahler chorale before ends on low F, triplets during the turnaround end on high F, meaning a two octave turnaround in four counts.
THAT'S exposure. All that Mr. Bruckner (great choice of name, by the way) pointed out is how the Bluecoats tuba book is written.