Yes but remember that Ueshiba himself came in contact with Daito Ryu Aiki jiujiutsu, when he challenged Takeda and was totally dominated by him, by his Daito Ryu techniques. And before this event Ueshiba was renowned as highly skilled and unbeaten practiser of MA. I'm not sure how well Mochizuki mastered Daito Ryu compared to O-senseis Aikido, but Daito Ryu is a complete MA and probably takes even longer to master that Aikido (if that's possible).
Interestingly, when Minoru Mochizuki went to France he was challenged by fencers, savate, wrestlers and boxers. He realized that Daito Ryu Aiki jujitsu was useless. So he changed to judo and kendo techniques and won easily. This is why he has added many judo and karate techniques to aikido. Upon returning to Japan he suggested to Ueshiba that he change aikido but he wasn't interested.
Mochizuki and Tomiki were the only ones who got Menkyo Kaidan from Ueshiba. At that time Ueshiba was teaching Daito Ryu.
As far as I know, none of Ueshiba's students reached his level of mastery. Its not surprising that Mochizuki as well as Gozo Shioda and Kenji Tomiki changed aikido to match their own ability.