Hello Dionisis
In the EIGRP over Frame-Relay lesson, we don’t have any frame relay map entries other than those created by Inverse ARP. This means that in that topology, the hub (or R1 as it is labeled) has frame relay map entries for both R2 and R3 (the spokes) but each of R2 and R3 have only frame relay mappings for the hub (R1). This means that the only option for routing here is via the hub, and this is why you see a next hop IP address of the hub.
In the example in this lesson, we have two statically assigned frame relay mappings in each spoke, including the broadcast keyword, so that direct access at Layer 2 between the two spokes is possible, and the next hop IP address can be that of the spoke router itself.
I hope this has been helpful!
Laz