Login item doesn't load immediately

Hey guys, here is the case:

1. I was planning to make my second disk (HDD) unmounted when I am not using it

2. I created a simple application to do this, called "Unmount disk"

3. I added "Unmount disk" to "Login items" under "Users & Groups"

Problem:
1. The app loads right after I login if I previously shut down my mac without checking "Reopen windows when logging back in"

2. The app takes about 30s to load if I check the box "Reopen windows when logging back in". Other windows load smoothly and immediately.

Question:
1. Is there a better way to achieve what I was planning to do?
NOTE: I also use "pmset -a disksleep 1" to make the disk sleep after 1min idle

2. Why does login items work like this? Any way to fix it? Or solve it?

3. I have also tried LoginHook, seems to work in the same way.

Also:
1. Wake up mac causes HDD to spin up, I use sleepwatcher to execute diskutil eject to spin it down

2. However, I found sleep watcher slows down the speed when turning off the machine.

Please correct me if I am wrong, and help me if you know something about this.

Thank you guys!

Best