Hello Brian
It’s nice to see how you are working through the problem and we can “read your thoughts” along the way.
So, having answered your own original question, here’s the question that I’ll try to answer:
You must remember one of the fundamental laws of routing: If a route is successful in one direction, it does NOT mean that it will be successful in the other. So R3 was able to communicate with R2 and R1 the route to the 3.3.3.0 network. So it is possible for R1 to reach R3. This is the perspective or R1 since there is a route from R1 to 3.3.3.0. However, if you looked at the routing table of R3 (which you did) you will see that there is no route back to R1 without the appropriate network commands.
So looking at the routing table in R1 only shows you that R1 can reach R3. It says nothing about R3 reaching R1. In order to determine that you’ll have to look at the routing table on R3.
I hope this has been helpful!
Laz