Some system variables are declared as AUTO_SET, and some of those also support being changed dynamically with SET GLOBAL.
For example, host_cache_size is declared as AUTO_SET:
But "autoset" doesn't work with SET GLOBAL:
There is special code to handle auto-sizing for this system variable (and others) at startup:
And you can explicitly specify to autoset the AUTO_SET option by using the --autoset option prefix:
Maybe it would make sense to be able to specify the "autoset" value in SET GLOBAL for variables that are declared AUTO_SET?