EOS (dPoS) reversed transactions multiple times while being top 10 at the time: https://cointelegraph.com/news/eos-reverses-previously-confi...
Ethereum Classic was attacked multiple times with chain reversing double spends due to not enough energy being committed to immutability: https://www.coindesk.com/ethereum-classic-attacker-successfu...
Ethereum reversed the "DAO hack" with a hard fork.
So yes, shitcoins are definitely mutable.
On a side note my colleagues are working on improving ETC against 51% attacks at the moment so hopefully that works out. Definitely wouldn't refer to Ethereum as a 'shitcoin'.
https://static.iohk.io/docs/etc/ecip-comparison-for-51-attac...
You know, this is quite ironic because cryptocurrencies are reaching a dead end, through their own flaws.
"Reality" is itself a fairly mutable concept if you're using that term to a refer to system that produces abstract "coins" with values that float against other world currencies in a system of finance that itself consists of multiple layers of indirection that evolved to solve the scaling problems of direct bartering.
Other blockchains are relatively easy to mutate and hence not good candidates for the World's reserve currencies.