I did not receive an email about the creation of T182538, the only reason I saw it was because Reedy's comment did send me an email. It does not appear that I was subscribed after creation or anything weird like that.
I do receive task-creation emails for other tasks. Mostly that's tasks that I get mail for via being subscribed to tags though, so perhaps it's something with directly-added subscribers or even subscribers that are only added via @-mentions in the task description? Although perhaps not, since I didn't get mail about the creation of T182478 either which is via a watched project.