Valve's gaming store Steam has separate ratings for "All Reviews" and "Recent Reviews". This makes sense in a market where products change significantly over time.
A bad game might've been patched into a good one and a good game might've added predatory monetization that people don't like. To be more useful, reviews should reflect recent developments like that.
The same is true for browser extensions. A buggy add-on can be fixed but the reviews will always be dragged down by negative ratings from that time. And a great extension can change owners or become abandoned which may warrant negative reviews.
By adding and highlighting Recent Reviews it becomes much easier for the user to gauge the current state of the add-on. It also gives add-on developers an incentive to improve their extension after negative reviews. And it rewards devs who keep their addons up-to-date and bug-free.
I believe highlighting Recent Reviews is a relatively easy and powerful way to improve the user experience on AMO.