Effects of test patterns
Both patterns are necessary.
AA/55 causes no net bus current in the transitions, pairs of lines are effectively differential, so there's no ground current in either driver or driven ICs. Alternating FF/00 causes maximum ground pin current, so is needed to test ground bounce.
If the tracks run parallel, then AA/55 excites them in odd mode, with capacitance to ground and the mid line between tracks, making them effectively CPWG traces, lower impedance than microstrip. FF/00 excites them in common mode, so capacitance to ground only, and an even higher impedance than equivalent microstrip. It's worth testing signal integrity with both extremes of effective impedance.