Why does :! open -a terminal or :! start cmd create totally new "applications"?

Question

Edit: on Windows, looks like it's opening in sysWOW64 instead of system32. Any ideas why?

Title. Basically, both of these commands are supposed to open a new console, the former on my mac and the latter on Windows.

For those familiar with Macs, you'll notice when ever you open a application multiple times, for example open chrome and hit cmd+n, it'll open a new window, but it's still under the same "application" on the bottom dock bar. Whenever I do open -a terminal, it seems to pop open a totally new application on the bottom dock bar.

For those familiar with Windows, you'll notice when you open many instances of chrome or a cmd prompt, they kind of get "shuffled" together, where you can hover on the taskbar to see multiple running instances of the same application; however, similar to my mac, it'll open a totally new cmd prompt, instead of "shuffling" it together.

What's the reason behind this, and do I have to be worried about anything?

Answer 1

On OS X, the open command (according to man open) acts "as if you had double-clicked the file's icon":

The open command opens a file (or a directory or URL), just as if you had 
double-clicked the file's icon. If no application name is specified, the default
application as determined via LaunchServices is used to open the specified files.

The man docs don't specify what happens when opening an application without a file (something like this from within Vim: :!open -a Terminal) but the behavior appears consistent with the described behavior about opening files – namely, that it opens a separate application.

I don't think there's anything surprising or concerning about this. Opening an application – such as by running open -a TextEdit from a Terminal window – should open that application (which it does).