What’s your opinion in this regard?
If we look at those areas where information was allowed to leak over the last hundred years, or so, since the obvious signs of suppression start to kick in (e.g Microprocessors, Quantum physics, Electronics, etc.), and extrapolate that back to areas where we have either not made any meaningful progress in that same period, or there are very direct and obvious signs of suppression (e.g. from just my own experience: Medicine, Cosmology, Atomic Structure, Nuclear Physics, Particle Physics, Standard Model, Multi-dimensional physics, Gravity, RF communications, EM Waves, Wave Mechanics and Holography, Signal Processing, etc.) I would agree that the implications and potential gains are truly mind-blowing!
But, I would also expect that their innovation and development would still be limited compared to the technologies that we
do see only because, by implication, if you limit the number of people working on a topic, you limit the opportunities for discovery of new and innovative ideas!
(If you look at the history of the folks that contributed to the last great push of unsuppressed research in Physics in the late 19th Century, you will see that Einstein was REALLY standing on the shoulders of a massive international collaborative community of giants when he took all their existing equations and re-interpreted them as Special Relativity!)
Compared to that level of collaboration, even if the PTB were able to skim off a few of the greatest minds of the day to work in secret on some hidden branch of physics, it would still result in a stunted level of development compared to the amount of innovation we see today - even using a model of physics that relies on pixie dust (dark matter, higgs bosons etc.) and fairy magic (dark energy, black holes, etc.).