No, you've actually said how you thought it worked, twice, but anyway: I'm not saying that it could not have been made better, because it could. It is cumbersome, it can cause headaches, and it can cause more than a few problems (for example, if you receive a phone call while your MicroSD card is unmounted and your ringtone is an MP3 saved on your MicroSD, you have to fix ALL your ringtones once you re-mount your card).
But what I tried to do was not giving you excuses, but explaining how and why things works a certain way, and this just because once you know HOW things works, and WHY they do not do what you expect, you can find easier ways to patch them.
One example: once you know that you need a sort of network between devices to have something that looks like multiple access to a device, you know where to look for a solution, for example by opening the Android market and searching for "wifi file transfer" or "network file transfer" and finding
this, or
this, or
this or
this.
I mean, once you (I'm using the impersonal you, not you as in you kennic) understand the mechanics, you know where to look for a possible fix/patch.
And while the apps linked above aren't the same thing as an (impossible to do) double physical management of the SD, it's the next best thing (and just as easy as accessing an SD via a networked PC).