Why did I receive a text message on my Mac prior to my iPhone?

Question

Since the Yosemite and iOS 8.1 updates, we can now receive our non-iMessages (SMS) messages on our Mac (more info).

However, the following strange scenario happened to me:

• I was using my Mac and my iPhone — just near me — was locked,
• the Message Mac app notifies me of a text message from my friend's phone (definitely not an iPhone user),
• 1 minute later, my iPhone vibrates and finally notifies me of the same text message.

Since my iPhone is the first and only device to get the text message from my cell phone provider, why did my Mac notify me first?

Answer 1

I think I understood and it's about:

I was using my Mac

When Apple knows we are using device X, it vibrates device X first so that device Y doesn't vibrate for nothing.

(even if device Y gets the information first)