Having physical memory segments be different logical sizes at runtime depending on the ECC setting does not sound fun.
Having your system’s available memory fluctuate up and down based on how many segments are currently set to ECC also doesn’t sound fun.
Having developers manually turn ECC off for regions where it’s unimportant sounds like a lot of complexity for a relatively rare use case.
There is in-band ECC in some newer Intel designs, but it’s all or nothing. Adding extremely complexity to memory management to selectively disable it sounds like a lot to ask.
I think your reading depends on thinking "application" means "process", while another reading would be that an application is a particular deployed system, where this setting can be altered e.g. at the BIOS level.
Having your system’s available memory fluctuate up and down based on how many segments are currently set to ECC also doesn’t sound fun.
Having developers manually turn ECC off for regions where it’s unimportant sounds like a lot of complexity for a relatively rare use case.
There is in-band ECC in some newer Intel designs, but it’s all or nothing. Adding extremely complexity to memory management to selectively disable it sounds like a lot to ask.