Finally, someone on the planet that has noticed this too:-)
I flagged this to Todoist support at the start of December. It took me several sets of email tennis to get them to acknowledge that there was a problem with the REST API.
I, like you, noticed that any natural language entry from Drafts, say, “paint door wed 9pm” would go into Todoist with the day/time, but not with an alarm/notification set, signified by the little alarm clock.
As I say, it took me many attempts to get Todoist support to acknowledge the issue. The last update I had (30 Dec) was that the relevant person was off and it would likely be resolved in “January.” I sent an email earlier this week to chase up, but have not heard back (par for the course for Todoist support). So hopefully it will get sorted soon.
At the moment, I just send the task names through to Todoist from Drafts until this is fixed.