Yes, as the program currently operates, subtasks are treated very differently than parent tasks. While they are located inside a task that is in a project, they don’t have the same status or value, so they aren’t technically part of the project itself. (They don’t add to task count or workload, they don’t appear on timelines or calendars, they don’t trigger rules, and they lack some other key capabilities of parent tasks.)
Meanwhile there is a very long thread about this with a lot more info, and you can upvote it below:
I know it’s not a solution and it is still a bit confusing, but some folks may have found some useful workarounds. We remain hopeful that the developers will add more functionality to subtasks soon.