I'm glad you raised this. I suppose that is one interpretation of my comment. The other is that we really need the extra functionality that Router Discovery does not provide. This allows packet duplication when at home. If it is valid between two foreign cells, it is just as valid between a foreign cell and a home cell.
Lets be consistent.
The alternative is that the MN recieves lower performance as it nears its home. That is silly. I would rather say that once you get home, you stop roaming. I am not keen on the packet duplication stuff, in general, but can see that it has some use. However, if we are going to include it lets be consistent.