They had guessed correctly. Ling Chuxi's cultivation had indeed not reached the Grandmaster realm. After being suppressed by the seal, she could only display the cultivation of the early stage of heavenly Yuan. However, Ling Chuxi was not as impulsive as they had thought.
She knew Ling Gusong's true intention. With his strength, he could defeat her in a fair fight. However, Huangfu qingjue and ye Wentian would never give him the chance to do so.
That was why he had proposed to use a single move to determine the winner, using the reputation of the Golden elixir sect to force him to make a move. If Ling Chuxi's cultivation was not suppressed, it would be impossible for him to win in one move. However, he already knew the situation of Ling Chuxi's cultivation, which was why he was so confident.