This is all true, but it's also reasonably common to make an exception in special circumstances, particularly where one of the authors made the key discovery, and move that author's name to the front.
For example, the recent papers on aperiodic monotiles have Dave Smith as the first author, even though his name doesn't come first alphabetically.
(I can also think of another recent example, which modesty forbids me to detail.)
In the case at hand, we did deliberately intend anon to be the lead author. (I was one of the ‘coauthors’ who helped to write it up.)
For example, the recent papers on aperiodic monotiles have Dave Smith as the first author, even though his name doesn't come first alphabetically.
(I can also think of another recent example, which modesty forbids me to detail.)
In the case at hand, we did deliberately intend anon to be the lead author. (I was one of the ‘coauthors’ who helped to write it up.)