Your Bluetooth card (mid-2010 iMac) is version 2.1
Low Energy feature is part of Bluetooth 4.0
So is Handoff.
And, Instant Hotspot also is provided with the Bluetooth 4.0 hardware.
And, your iMac says "No" to all those features, because no Bluetooth 4.0 until the Late-2012 iMacs.
So, not defective, just not supported with the older bluetooth on your 2010 iMac.
more info about those BT features:
https://www.macrumors.com/2014/10/23/how-to-instant-hotspot/
If you want to pursue updating your iMac to support Continuity - I did find
this info