Being a retired transit bus driver, I would have a problem with a forward mounted mirror on the left side ...or one that you view out of the corner of the windshield. You will notice that all transit buses, OTR buses, and most (but not all) similar commercial buses will have the left mirror mounted on the side.
The reason that buses use this configuration is that the goal is to have the mirror as close in distance to your eyes. The further the mirror is physically located in relation to your eyes, the less area is viewed in the mirror glass itself. It will usually not make a huge difference but that is mainly why you'll see buses with side mounted left mirrors. For me, driving buses for as long as I did, I purposely chose a motorhome with a side mounted left mirror. At one time, I test drove a Newmar with a forward mounted left mirror and it bothered me.
And yes!! Your are definitely correct in that, again for commercial buses, the goal is to have the left mirror head itself as close to the side of the coach as possible. Again, observe any city transit vehicle and you will not see the left mirror sticking out any more than a few inches from the side of the coach. I cringe when I see these Class A motorhomes with their mirrors sticking out a foot from the side of the coach. Not only is it asking for a truck to come by and knock if off but it also makes it easier for the motorhome driver not to hit the mirror head against a fixed object when maneuvering in tight conditions ...or in parlance of transit agencies, "you make the bus wider the further you have the mirror head from the side of the coach ...adjust the arm so the mirror head is as close to the side of the coach as possible." Unfortunately, on some motorhomes, the mirror arm itself may not be adjustable.