Riff this is a very wise move especially after the CH-53K transmission embarrassment.
The 53K MRGB is also a fairly complicated design, but in a different way than the S-97 MRGB. The 53K has three engines driving a single main rotor, while the S-97 has a single engine driving two main rotors.
I would not necessarily consider the development problems with the 53K MRGB an embarrassment. It is a (12 way) torque split configuration designed for very high power (>16,000hp) and low specific weight (over 500lbs less than planetary config). Torque split designs are notoriously difficult to get right because the multiple load paths present a very complex analysis case. The 53K MRGB relies on torsionally compliant quill shafts and precision assembly to provide the required balance of torque distribution among 12 pinions driving the bull gear. Anyone that has experience working with this type of gearbox would agree that getting the torque balance correct requires a detailed analysis effort plus several cycles of bench test/design modification.
The only reason Sikorsky might have to be embarrassed is if they failed to fully appreciate the level of development effort this type of gearbox has historically been shown to require. I also would have expected NAVAIR to foresee these kinds of development issues. NAVAIR has some very competent people and have lots of experience in this field.