The Jews thought that the manna was a gift from Moses.

“there arose up three good providers, or pastors for Israel, and they are these, Moses, and Aaron, and Miriam; and three good gifts were given by their means, and they are these, the well, the cloud, and the manna; the well by the merits of Miriam; the pillar of cloud by the merits of Aaron; the manna, by the merits of Moses.”

T. Bab. Taanith, fol. 9. 1. Seder Olam Rabba, p. 28. qt’d in Gill

Jesus dispels 2 misconceptions of the Jews here: He tells them that it was not Moses, but God who gave them the manna; and that what their fathers ate was not the true bread from heaven, but just an earthly type of it.

Jesus used “has given” to describe the giving of the manna and “gives” to speak of the giving of Himself. God is even now giving them the true bread from heaven of which their fathers only received the type.