For each snapshot of 1.13 I have loaded a new world and have gone to the end looking for cities... They seem to only spawn in the negative negative quardrant (North-West) and in no other direction.... So none have spawned in the +, +-, or - areas of the end... even when they do spawn only about 8% of the end cities I have found that have ships are cut in half where the elytra should be.. I did however figure out that when I went past -20,000 blocks in the end I started to see more and more ships that were still broken partially but still have the elytra there...