I’m not sure Rubio has control over his delegates the same way Kasich does (at least on the 1st ballot).
Did Rubio officially withdraw from the race or suspend his campaign? If he ended his campaign, his delegates may no longer be officially bound, but may new be uncommitted delegates on the 1st ballot.
He only suspended. He specifically wrote letters to states saying that he expects his delegates to stay bound to him.
His statement yesterday was a verbal statement that he “expects” or “hopes” that his delegates will vote for the only Conservative in the race, and at this point, that is Cruz. He meant after they become unbound. He wasn’t talking about changing their binding to a different candidate. He was merely sending a signal to his delegates that he is #NeverTrump, and he hopes his delegates will vote for Cruz on the second ballot (or whenever they become unbound).
It was also a signal to Cruz that he would consider the VP position.