However, Ethereum has a built in "difficulty bomb",
"difficulty bomb" is more like a scarecrow specially because of its name. in fact they messed it up when they pushed it back a couple of times since this hard fork was supposed to happen a very long time ago. which proves it is not really a big deal. not to mention that Ethereum Classic (the original immutable chain) got rid of it about 9 months ago which means if anybody wanted they could simply pull the already tested change from ETC into ETH and continue mining in.
You should call it as an upgrade, not hard fork.
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they are not two different things. an upgrade is a hard fork, calling it something else doesn't change its nature.