@mano: with a heading reference you link to the # heading, so making a change to # heading will affect the link.
With a block reference you link to that tiny ^number, which is not affected by a change in the text of the block. If you were to change that tiny ^number you’d find the link is broken too.
AFAIK auto-update links to headers has never worked because it has not been implemented, but it is supposed to be one day, though I don’t know when.