I come from running background and I was use to do 10x800m with 400m easy jog in between on track

Coming into triathlon, especially from IM athletes, I noticed that it is very common to see 800s intervals with 30" passive rest, standing still.
In my opinion with only 30" still rest, they are very tough especially first or second time you try

In general, what is the difference between the 2 sessions? which one is better for LD tri training?