DDR5 supports on-chip ECC but the extra parity bits we typically associate as "ECC" are still as optional as ever, motherboard manufacturers will still not bother to route those signals anyway, and Intel will still demand you give up overclocking and pay more for Xeon in order to use ECC sticks.
I did some reading up on this just now. You are of course right in that ECC on-chip will only handle bitflips inside the chip. To ensure the integrity of signals between the memory and the processor traditional ECC will still be required. On DDR5 it will be necessary to have 4 parity chips whereas with DDR4, you only need 2, so true ECC capable memories will be considerably expensive.
> you give up overclocking and pay more for Xeon in order to use ECC sticks.
That's my point, a virtuous monopoly wouldn't do that. It would allow at least some way to have both. Especially since soft errors are easier with smaller transistors.
Agree 100%. IMHO, the choice between "domestic" and "industrial-strength" should not mean choosing between different degrees of risks of failure.