Lumia 520 is not hardware capable to support Glance. Or is it?

This is just pathetic. I was direly waiting for Glance Screen on my Lumia 520 until I saw the unfortunate announcement that all Lumias except 52x series will get the feature as those phones don't meet the hardware requirements.

I bought that excuse, until I came to know that even the Asha 501 has got the Glance Screen as well! After some investigation my prior suspicions came to be true that Glance needs ONLY the proximity sensor to operate and nothing else. So WHY? Why the Lumia 520 with the proximity sensor is not allowed to have the Glance Screen feature?

I didn't expect this from Nokia. There is absolutely no reason to leave out this amazing feature when the phone is perfectly capable of handling it. Is this partiality from Nokia's side or am I missing out on some important info regarding the hardware?