You didn't elaborate on AWD.
A 4WD doesn't have a centre differential, so no need for a "centre differential lock", but a AWD could be fitted with a "centre differential lock".
Axle differential locks are helpful, but 'recirculating power' or 'binding up' can happen between the front axle and rear axle on a standard 4WD, it is not exclusive with the fitment of a diff lock,

Naturally I couldn't write everything there is to know about 4WD and I'm not a mechanic. This was written for those who have little knowledge of 4wdriving and a basic, simplistic breakdown of some things to look at - some vehicles like Lada Nivas and Range Rovers have these centre diffs as part of their mechanics. Appreciate you comments and time to make things clearer to others. Thank you very much.