It really depends on what you want to achieve. In the specific example you are referring to, Rene is filtering out anything that matches the first statement, that is, anything within the 172.16.1.0/24 network. This means he is denying traffic matching this statement. You must remember that like access lists, prefix lists have an implicit deny statement at the end. This means that if the prefix list had only the first statement then, anything matching the 172.16.1.0/24 network would be denied, and then, everything else would be denied as well.
For this reason, the second statement was included, permitting everything. Now this statement is only necessary when you want to deny traffic that matches a very specific criteria, as is the case in this example. If your purpose is to permit traffic for a very specific range of addresses, as Rene did in a later example, then you don’t need the permit statement at the end. Indeed you mustn’t include it, otherwise your prefix list wouldn’t work correctly. For example, take a look at this prefix list:
R1(config)#ip prefix-list RENETEST permit 10.0.0.0/8 le 19
It is used to permit only networks that fall within the 10.0.0.0/8 range and have a subnet mask of /19 or less. Everything else must be denied, and everything else is denied because of the implicit deny everything at the end of a prefix list.
I hope this has been helpful!