My employers travel policy allows for Premium Economy on international flights over 6 hours. An improvement on a previously Economy only policy. Anecdotally, I understand some other companies have shifted in the other direction from J to W.

In the past 12 months, I’ve done 8 return trips in WT+, so 16 segments. All were completely full in that cabin bar one flight which had a solitary free seat.

So from that perspective it seems to be a popular enough cabin to travel in. But agree with others it’s likely not a popular cabin to redeem Avios for.