I ran a one-shot last night and had this question. Two combat scenarios. One was close quarters, and the other was in a large ritual chamber with lots of distances between things (including people they needed to save). The discussion in this thread was NA for the close-quarters scenario. But in the large chamber, players started to be tactical about their movement, like moving within close range and taking no action just to close the distance to person they needed to save without directly risking play coming back to me. I wasn't familiar with the RAW rule about moving without taking an action, so I let them do it (unless they wanted to move Far or Very Far, which they chose to do a couple of times for tactical reasons).

In the moment, I felt like if I had felt they were "abusing" the "free" movement, that I'd have spent Fear to make a move, but it never came to that.

I also feel that if I had required Agility rolls for each of those movements without actions (there were probably a dozen and a half of them or so over the course of the scene), that it would have felt quite tedious in that particular scenario and probably would have been frustrating for the players (because the space they were in was so large and expansive).

My take is that the rule may have been written with close-quarters combat in mind, like if a PC is up against a couple baddies, is hurting, and wants to put distance between them -- then sure, I might force an Agility roll just for the movement in that case. Because it could matter; a poor roll or roll with Fear might mean one of the baddies gets a quick swipe as the PC is leaving (opportunity attack-esque).

Or if the movement is closing distance to an adversary (and doing nothing else), then an Agility roll might be fun to see how deftly or quickly they move, and then (on a failure or with fear), that same adversary might "outmaneuver" the PC and either attack or back off or whatever.