I I'd say that I did go in front of my horse when it was tied. they were the reasons I thought might be why it says not to go in front of your horse.
I can understand about not tacking up in a stable if the horse doesn't have one, I am asking why all the 'thing' about cross ties.
I would collect my tack, take it to the horse's stable, saddle on the door, remove its rugs (blankets), flick it over with a brush, bridle then saddle. Unless it was a young horse I was just starting I never tied them.
When I returned I would untack, take the tack to the tack room, most of mine would roll when they got back, then on my return they were given a good groom, rugged up and left.
I rarely tied any of my horses, not even for clipping, as they would stand where they were told.
As I was always busy I did cut corners with many things like tying them up but I knew the horses well as they knew me and there was trust on both sides.