Ok.
Nobody answered my question.
so, I researched the block timestamps in Bitcoinwiki.
They say it may not exactly accurate.(Block times are accurate only to within an hour or two)
https://en.bitcoin.it/wiki/Block_timestampTimestamp order is not important.
My problem solved.
It's what I posted in my first response to you (clock drift) - it is working as intended. However, I don't recall seeing a 2 hour difference between specific blocks within the last 11 entries which is why I asked as well.
In the Reddit, imperdin said "Attackers are using a nefarious pool that injects malicious time-stamps into blocks to forcefully reduce the difficulty to mine blocks at a faster rate at the expense of others."
I think this is right because I could not find which pool found from block 66311 through block 66369 in the graft pool list.(
http://grftplst.zarub.org/)
Therefore, In the spacepools, a Nicehash buyer spent a lot of money for one block.(effort 9431% for one block 66375)
66375 34 / 60 933201974 16d2307190616728ec8fec0e8472dd04d91c0cb79fefc6392ee8181a00b4bdf0 TBA 4/20/2018, 9:17:14 PM 9431%
https://graft.spacepools.org/#pool_blocks