That is not entirely true. Binaries in the packaging systems might not be compiled for the most recent atomic instructions which can really affect performance.
Well, that – yeah. But it doesn't strictly have anything to do with the actual CPU model specific tuning that the news was about, only in that setting a specific CPU in -march (-mtune would not do it!) would imply the features. Typically though you'd just do -march=armv8-a+the+desired+features for that like the first post you linked does.
Really the important piece for making distribution binaries not suck is ifuncs/multiversioning. But library and app authors currently are required to deliberately use them. Which is fine for manual optimizations that use intrinsics or assembly (and e.g. standard library atomics) but I'm not sure any compiler currently would automatically just do that for autovectorization.
https://blog.dbi-services.com/aws-postgresql-on-graviton2-aa...
https://github.com/microsoft/STL/issues/488
We are about 9-14 months away from the right pieces making their way through the software ecosystems where this will be almost a non-issue.
Exciting times for everyone!