It is not true. Wallet feels fine even on old processors.
I find it works great staking on old processor too, even virtual machine. However I think there may be some problem if the amount of UTXO in the wallet is very large. Because, all those many amounts trying to stake separately...
The code for staking is at https://github.com/EvgenijM86/emercoin/blob/master/src/wallet.cpp in function CreateCoinStake. But I don't know enough about C++ to understand all implications.
Hopefully K1773R can explain more about his problem. And if there is a problem for some situations, then perhaps the team will investigate the cause.
Unfortunately this problem is ignored. may it be due to bad English skills or ignorance, it still an issue and others will hit it too.