It's interesting tho because Vegeta only thinks Goku was no SSJ because he didn't show to be ruthless. Other than that, he believed Goku was the legendary warrior, as did Ginyu, until they saw Goku wasn't ruthless. Vs Jheese, he didn't say he was a SSJ yet, he said he was in the path to become one, while he discared Goku not because of his power, but because of his attitude.
But still, since not even while rivaling 1st form Freeza, Vegeta considers himself a SSJ and only does so after the Zenkai, it seems he just didn't consider the power shown by Goku there (~60,000) as enough to be a SSJ later on. Seems like he chaged his idea on it. It's also weird because he expected Goku to be a SSJ there when he knew Goku was no match for Freeza... And he considered the SSJ to eclipse Freeza. So there seemed to be a flip flop on Vegeta's idea regarding the power needed to be a SSJ. He was likely somewhat caught in the shock by Goku's sudden power and growth, along with his clamness, and then when reaching and surpassing that power he may have seen it still wasn't SSJ like.