The Dark Imperium Intercessors and other sources of monopose and easy to build Intercessors all come with the rapid fire bolter. Most of the intercessors I have seen at tournaments have been those and would explain why so many use them.
I only have the intercessors from the intercessor box so I never glued the scope/mag and just use something similar to bluetack to keep it on. Already a tight fit so they wont fall off. Right now they are all carrying the assault version but I have a little box with the rapidfire parts from before the point changes. If I decide to use the heavy/stalker versions one day I would only need about 2 hours to clean, undercoat, paint, varnish and replace 20 rifles.
Havent seen anyone else in person actually bother with this so could explain why you see the rapidfire version more often in tournament lists with strict wysiwyg
even if they would have prefered the assault version. Think this have more to do with it than an meta choice against marines. Not that much of a difference and most people are too lazy to buy and paint up 5-10 more intercessors for such a tiny advantage. An advantage so small you probably wouldnt even notice it even over a whole tournament.
Do people really host tournaments with such stupidly strict WYSIWG rules? The difference between an auto-bolt rifle and a regular bolt rifle is small, the difference between stalker and regular is almost impossible to tell. If you're using the right model, it seems to be one would have to be a real dink to care about brass tacks of the weapon loadout.
I like my stuff to be WYSIWIG to a reasonable degree, but I'm not
buying a new Repulsor just because GW
changes the weapon stat lines. it's a repulsor. You don't know what the weapons do anyway unless you're another primaris player, so just look at my army list if you want to know what its got.