5 new hot nodes were added, but the relocating shards were all freeze nodes, and the number of freeze nodes was close to equilibrium. ES version 6.8.3
awk '{print $ NF}' 2005_shards | sort | uniq -c | grep freeze | sort -k 1 -n
261 data-202-freeze
261 data-203-freeze
261 data-205-freeze
261 data-206-freeze
261 data-208-freeze
261 data-209-freeze
261 data-211-freeze
awk '{print $ NF}' 2005_shards | sort | uniq -c | grep hot | sort -k 1 -n
3 data-224-hot
3 data-225-hot
3 data-226-hot
3 data-227-hot
62 data-07-hot
63 data-16-hot
The index is only set the require zone. It should not be reasonable. Hot node should be balanced first. At least the number of node fragments on the freeze is balanced. It may be that the single index is not balanced because the index shards per node is too large.