It looks like a probelem of diagram update logic working in viewDirectionAlignedWithModel
= false conditions... Yes, you can modify ??diagramUpdater to handle this
situation properly.
BTW, if you just need to create link from node1 to node2, but show it with
an arrow pointing to node1 then you can use source decoration instead of
target in .gfmgen model and visually link will point to node1 (staying alighed
with model link in notation model..)