I’m going to AIT later this week to renew my passport and noticed that they prohibit certain items like laptops, cameras, large bags etc etc. But, then below that they mention personal electronic devices such as cellphones, smart watches and it’s very unclear as to whether or not they allow those in. They seem to imply that they don’t, but they don’t say they are prohibited. The whole thing is very vague and confusing.
Has anyone recently been there with their phone?
Not recently, but when they were still on Xinyi Rd., phones weren’t allowed in; you had to check your phone at the door.
That’s ok. Because for prohibited items I heard they will not allow you to check them. Thanks!
You’ll just have to leave your cell phone with the security guards.
This exactly from my experience. However, do not bring any food / drink. They won’t keep it in storage for you, they will make you throw it away / pour it out. RIP the pack of gum I bought at PX mart a few minutes earlier 
Went to AIT last March at to renew my passport. I wore a backpack in and had a small coldbrew bottle of coffee with me which they didn’t seem to mind. They check your phone through security but they don’t hold on to it.