I always feel like saying something can be done in "2 minutes" is more like, "it can be done fairly quickly, needs no other input or research, and the only thing stopping me is that it's boring or I'm feeling lazy"!
To take a silly example - if I need to write a short letter to my gran, just to say hi I might put it off because I'm a terrible grandson

But applying the "2 minute rule", I would say it's something I can do immediately, needs no external help or information, and I should get on and do it. Even if it might take longer than a strict 2 minutes, it's a relatively quick uncomplicated task that can be done NOW.
Similarly, if I need to call my mobile phone company, I know I'll probably be on hold for a while which might take longer than 2 minutes. But if I have a bit of time, I'd just do it straight away - it doesn't need any more input, the only thing stopping me is that it's a hassle.
Using the 2-minute rule like this I find is quite handy, because it shakes me out of my "I can't be bothered" mind-set for tasks that I can put off, but should really get off my bum and do!