There is a more detailed press release at
https://www.eurekalert.org/pub_releases/2018-07/iu-srt073018.php
The whole thing seems to be based on theoretical modelling with some assumptions being made because of a lack of information about the physical properties of the pyramid. It's those assumptions which bother me - if any of them are wrong, that will affect the results.
The EurekAlert piece says "Scientists predicted that under resonance conditions the pyramid can concentrate electromagnetic energy in its internal chambers and under the base." Surely the obvious way to confirm the results is to go to the pyramid, set up detectors inside the chambers and then throw a lot of electromagnetic energy at it and see what the detectors find ? My guess would be nothing much, though I'm sure there would be plenty of people around who would come up with endless explanations as to why.
I'll mentally file it in the same folder as phlogiston and flying saucers for now.
It would be interesting to see jim360's take on it after he's read the paper, but I suspect he may not have the time or inclination to do so.