Hello Marios
In the description in the lesson, Rene mentions that IGPs in general calculate their LFAs using different methods. Now EIGRP always calculates an LFA, which is called the feasible successor. And EIGRP always computes prefix-based LFAs. This is something that cannot be changed because it is an intricate part of the routing protocol itself. This is also confirmed by this Cisco documentation where it states:
EIGRP always computes prefix-based LFAs.
So far, when talking about LFAs, EIGRP, by its very nature, performs this function, and it only performs it on a per-prefix basis.
The further configuration done in the lesson simply enables FRR, which means the feasible successor, whichever one EIGRP natively chooses, will be placed as a repair path using the fast-reroute per-prefix command.
The fast-reroute load-sharing disable command, is used to disable the default behavior of FFR which is to load share across LFAs if they have the same metric. If this is disabled, then the tie-breaking rules will be applied and only a single LFA will be installed as the repair route. More information on this command can be found here:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/17-3/command_reference/b_173_9500_cr/ip_routing_commands.html#wp1624013282
Now other routing protocols, such as OSPF (depending on the platform and IOS version) do support per-link LFA. For more information on LFA FFR for OSPF take a look at this lesson:
I hope this has been helpful!
Laz