Stride length confusion

I've been really confused about something lately.
I recently read on Instagram someone who said her coach told her to shorten her stride when she runs, and that it would help her, and she said it really has.
 I thought that sounded interesting. I remember hearing that in order to run faster, you need to lengthen your stride. Now, I'm 5'11, so I think I already have a pretty big stride, and that's never seemed to help my speed!

But, I thought what could it hurt, I'm going to shorten my stride when I run, and see if it helps.
I've been doing that this week, and it really seems to help! I'm not sure that I'm much faster, (although Saturday's 5k was pretty fast for me) but I can run a much longer distance without feeling like I need to walk. I feel like I have more energy and don't need as many walk breaks.

It seems like shortening your stride would have the opposite effect, and you would lose energy because you're taking more steps to cover the same distance.

Does anyone have an opinion or experience with this?