I think you're probably right on the money with this one. When I was in high school, we did the same workout but with 3:00 rest, and our coach even quoted the international coach Dr. Rosa as having his athletes do this workout in the past.
The one argument I would make with what you said though is kind of one of semantics.
It could be that maybe the OP and other runners recently did a 5k which would probably be slower than their track 5k pr. Even if they haven't raced a 5k in a while, their CURRENT 5k pace is probably much slower and probably more like what their 8k pace will be later this season.
So when the coach is suggesting 4 x mile @ 5k pace, it possibly doesn't mean their 5k PR pace but what they could run for a 5k right now, and that might be more do-able.
For instance, if my 5k pr was 15:35 (say 5:00 min/mile), but after the summer my current best today for 5k is say 16:20 (say 5:15 min/mile) do to different training, then I could see where the coach wants his athletes to the 4 x 5:15 min/mile w/ 1 min rest as opposed to the 4 x 5:00 min/mile w/ 1 min rest.
I still agree with what you said, but I'm just questioning what exactly the coach of the OP means by 5k pace: 5k PR pace or CURRENT 5k pace? So I suppose this is more directed at the OP who is the only one who would know the answer to this question for sure.