As far as I know there isn't any direct reason why this would make uploading harder; it's a non-computational element. But the fact that it took so long to discover it does mean we should expect to have missed more things.
I saw a fun talk at a conference in December where Jeff Lichtman showed us some of his processed data from his 5x5x30 nanometer resolution mouse brain tissue electron microscope scans (of which probably a 30 micron wide cylinder was actually properly annotated). He mentioned that only 40% of the things-that-were-clearly-synapses in the annotated dataset were the large spine-based synapses that have been well studied, and that there were a couple cells in there that he had no idea what they were at all.
Kipnis et al found a new part of the lymphatic system. It goes into the brain.
The fact that we still get surprised by new elements of the brain suggests that there quite a lot we still don't know about the brain and uploading might be harder than previously believed.
Given that these vessels were hard to find, it will be interesting to see whether other hard to find vessels will be discovered in the coming years.
Besides their Nature article Structural and functional features of central nervous system lymphatic vessels, there a good article on NeuroscientistNews titled Missing link found between brain, immune system -- with major disease implications.