On further investigation, I see my blog was set to "immediate" instead of "asynchronous". However, if so, then why did b2evo say "scheduling asynchronous notifications" after I saved the future-post? It's confusing. If the blog is set to immediate then how can it be scheduling asynchronous for later? At this point I don't know if my blog should be set for 'immediate' or 'asynchronous'. I plan to post 50% NOW and 50% future-date, so which one should I select?

There is also an error in the scheduler for that future-post, which says "Send notifications for <blog post title>" -- ERROR

The error details for the failed notification says: "Post notifications are not set to run as a scheduled task."
However, when I try to add a new job, I see what's shown in the screenshot. None of them say anything about "Send Notifications" so which one is it?

Here is the error info. Cron is set to run at 11

If you post in the future at least once in a while, you must set your notifications to Asynchronous. (Agreed there should be a warning message when you post in the future but your notifications are set to "immediate".)

The scheduled jobs will be created automatically each time you publish a post.

Ok, so is the cause of the error specifically because it was not set to asynchronous, or is there something else that could also be doing it? All my other scheduled tasks seem to work properly so I don't think it's the scheduler setup itself...

Yes the cause of the error is specifically because it was not set to asynchronous

Additionally, we made a better warning message in b2evo 6.6.6: