They litterally did the same for Tears of the Kingdom, before realizing people were thinking that if they don't show anything that means the game has nothing to show for, so they tried to put more stuff last second
You are correct, I had forgotten how secretive they were of Tears. But we did get a final hype inducing trailer after the ho-hum reveal showcasing the fusing and building elements of that game. So we are due for a similarly hype inducing trailer for Prime 4 hopefully within a couple weeks.
For the folks whining about the gunplay in Beyond…
Did you play Corruption?
Did you watch the boss fight at the end of the demo?
Do you realize the emphasis they are putting on the GYRO and/or mouse controls?
Lets recap.
Prime 3 Korrupshun featured some of the greatest combat to ever grace a Metroid game. Dare I say on Hard mode it bested many, many FPS games and created a glorious fusion of arcade style light-gun styled aiming with full movement. This was due to the focus on the IR pointer controls and lock-on free aiming. A far more advanced version of the typical down the sights aiming used in most FPS games still to this day.
In nearly every glorious boss battle and many enemy encounters, you had to be able to dash, move, jump, grapple, and shoot down multiple targets within seconds. Take the Rhundas battle for example, which is still an early battle in the game. He has an attack where he shoots out multiple homing ice blasts and after doing this he is chasing after you and shooting bigger ice blasts. Each homing blast has splash damage which will freeze you even if its not a direct hit.
You had to dodge some, shoot the remaining blasts in mid air, and charge towards rundas afterwards and start blasting him. On top of this you needed to utilize and manage the korrupshun mode to deal serious damage.
Prime 4 already shows these mechanics being used at the end of the demo against the boss. Which is a great sign, because it took Prime 3 quite a while longer for the combat to show its potential. They teased it during the first Ridley battle, but that was more on rails since you were fighting him in mid-air.
I think its safe to say Beyond will push these elements of combat in addition to whatever new abilities even further.