I think what it's saying is that it may very well happen, and may be great for those 4 cities, but that it won't impact the rest of the network much - you could connect to the LSL in Cleveland or the Cardinal in Cincinati, or what ever else is going by then, but their modelling doesn't show much of that, they expect this to be a locals mostly thing.
I really hope this connection is going to happen. I'm interested in visiting Cincinnati one day. Currently, as already mentioned, there are so few connections and they are in the middle of the night. Columbus having no passenger railway service would also be unthinkable in Western Europe regarding its size.
For me the Cleveland-Cincinnati connection could also help the network a little bit as you could also connect Indianapolis with Cleveland (although you would have to change trains in Cincinnati, but better than nothing). How much time would a trip from Indianapolis to Cleveland via Cincinnati likely take?
With this connection, Cincinnati could eventually be linked with Pittsburgh and Buffalo, via Cleveland.
Additionally, the Toledo-Detroit connection seems interesting for me as well. According to my geo portal, there seem to be in minimum 4 different tracks running directly northwards between those two cities. Could it not be possible to acquire one line completely from the freight companies? Is there somebody here who can give me an explanation for the situation there?
Indeed, I would like to see an additional line from Saint Louis to Indianapolis as well. But unfortunately, I guess it seems not to be under serious consideration by Amtrak as its not in their infrastructure plan.