I'm not actually convinced by either argument. A lot of our train stations have physical barriers you must scan a transport card at to open (or just jump), but Broadmeadows doesn't - it's just a little standing receiver that you can ignore. The track on the right is often used by freight trains which do go fairly fast, so that potentially makes a small bit of sense (the rest of the platform is fenced off from that track too) with the left track being primarily used by passenger trains stopping at the station

However these fences don't do much to fix suicides either, because we do not use platform screen doors in Melbourne so you could still just jump onto the tracks, and there's another track next to the freight track on the right which has a platform you can access so you could jump off of that one and in front of a freight train too

So the only actual advantage I can see to having it like this is that in means there's only 1 (official) entry/exit to this platform, so ticket inspectors could just stand there and find anybody who doesn't touch on. However our ticket inspectors tend to congregate more around universities and they also tend to ignore people they profile as likely violent/loud types, so they would barely do anything anyway