Showing a form does not indicate if the account creation is blocked or stopped as all checks are done after the submit.

For a local ip block the form is also shown and fails after submit, so this task could be rewritten to be more generic.

In T342574#9039360, @Umherirrender wrote:

Showing a form does not indicate if the account creation is blocked or stopped as all checks are done after the submit.

For a local ip block the form is also shown and fails after submit, so this task could be rewritten to be more generic.

In previous versions of unknown date, the form would not be shown at all, instead having an "Account creation error" or "Permission error" shown. This seems to me to be a rather bad regression; MediaWiki never shows a form for an action that you're not allowed to perform at all.

rMW04bdfa50f0fd: Fix block handling in CheckBlocksSecondaryAuthenticationProvider and the merging of global blocks into normal blocks (T257701) are two relevant changes I'd look at. At a glance the code seems correct, though - global blocks are hard-wired to prevent account creation and as they are now unified with normal blocks, they should have the same effect as local accountcreation-disabled IP blocks.