King Elbas knew that the situation was getting rough even before his companions suffered significant injuries. He had reached the point when he had seen enough exchanges to predict the rest of the battle, and he didn't like the direction of his thoughts.
The experts had reached Noah's conclusions. King Elbas knew as much as him, so he could see the issues in Heaven and Earth's current behavior. The rulers were hiding something, and his team didn't have enough firepower to draw that out.
Of course, King Elbas acknowledged the likelihood that Heaven and Earth couldn't use their true power. Everything was possible with a quasi-rank 10 being aiming to complete its breakthrough.
Heaven and Earth could have decided to save energy for multiple reasons, but King Elbas remained quite sure that they were playing with him and his companions. It simply didn't make sense for such a strong being to be unable to do more.