Yes, you are probably right since from a cheap point of view when it boils down to manufacturing parts it would be far easier to get a bulk supply of 20 foot threaded rods and to simply cut them down to size for the various lengths on the mounts, exhaust, and intake. The catch is to make that process cheap you need to be able to cut the stuff easily, and therefore soft.
That left side rod with the blank shoulder takes more time to make, and it makes sense not to cut threads to the entire length if you are dealing with hardened steel, only cutting half the rod means twice the life on the tool. Probably upgraded due to complaints from distributors.
Now what I can't get past is that you can get hard high grade steel at various places and often the steel has that nice gold tint to it because of the type of metal it is. Now I see manufacturers apparently like to paint on a shellac of gold tinted color on plain cheap steel nuts and bolts, and the stuff flakes right off, why they pick a gold color is beyond me but seems a little sleazy to mimic a good steel by painting cheap stuff a different color that matches good stuff. I know it's probably just a coating to prevent rust but then again why install it in an engine exposed to the environment if the coating is going to come off and rust anyway?
Maybe I'm thinking about it too much but really...
I also must say I've seen shouldered bolts but not in a bright silver only, they also come galvanized and coated in paint so thick that threading a nut on them feels suicidal. They also come in rust spotted and bent. My first kit (gasbike) came to me with 2 bent mounting studs which probably happened during shipping, I attempted to bend one back and it immediately snapped off at the hole. Now that had a shoulder, and if it was stainless it probably wouldn't have snapped from being bent 10-15 degrees off straight and then being bent back under hand strength. My ez-out kit drilled it and removed it quite easily too, so it wasn't strong stuff at all.
At this point I've resolved to just replace the bolts from the get go with grade 8 black oxide Allen head bolts or try to use bright stainless since it won't rust.
The best bet against all breaks regardless of the steel is proper torque and maintenance, if you let it get loose the engine will conceivably break any stud by shaking the crap out of it. If you use locknuts and blue threadlock and tighten the mounts only enough to keep the engine solid then you will probably have no problems. And if you are doing that put threadlock in the engine mount holes and put the bolts in, this way nothing can back out and get sloppy.
The problem I have most with is an exhaust or intake bolt stripping when I put the nut on, it seems that either the nut or the bolt strip under pressure if it's the cheap stuff. I probably over tighten it since my torque wrench doesn't usually fit in those places. The only saving grace is when you use a soft bolt on those places you'll be more likely to strip the bolt than stripping the holes in the cylinder, which to me is more favorable since replacing a small stud is easier than pulling an entire cylinder to helicoil it. I personally think that putting a helicoil in the mounting holes right off the bat is a good idea but for most people it's probably overkill.
Oh the woes of the happy time motor...
