You should read it carefully, instead of just bolding the bits you like.
"no statistical difference between groups for the bench press of parallel squat."
So, both groups ended up just as strong. It's just that the periodisation group's strength increases were more steady over the period, while the progressive group reached their top strength before the end of the period and then plateaued.
Which suggests that complete beginners need a progressive programme, while experienced lifters need periodisation. Put another way, simple progression gets you stronger quickly, periodisation will get you there but with more stuffing around.
These are not, I think, new ideas.
And,
"Volume of work performed was more powerful in determining strength than was the manipulation of repetitions, sets, or periods of active rest."
In other words, the way to get stronger is to get under the iron and bust your arse, rather than worry about exact sets, reps, and so on. Again, not a new idea, but always nice to test these ideas just in case.