Okey, I m now on the same page as yours.
Probably we need to understand the bit of “old story” how the Appsheet was developed and new feature added.
In this context, let me talk about the main menu etc.
On UX and options we have this setting.
When we turn off, the main menu looks like this.

The share button always the upper left, sync button upper right.
This has been default setting and view, i.e. the share button can not be hidden and always upper left, while sync button always upper right, since Appsheet by nature.
I can not remember when it was, but not long time ago, the Appsheet introduced the new main menu setting, which probably most of user is currently setting up in that way. I mean turn on this setting.
By doing so, the sync button move to upper right, and share button move to Menu.
Then now we are able to utilize the max 5 view on main menu navigation without interrupted by share and sync button any longer after that.
The article you mention about share button seems to be not updated, but written at the time when new setting for main menu navigation bottom bar was introduced. However, it is still valid. Meaning, the share button was located in the upper left on the bottom ALL THE TIME.
Based on that OLD setting, hit the share button. If we are not opening up detail view, the email template body will have sharable link to app . But open up any of detail view, then hit the share button, then you will see the linktorow type of url, i…e when the link is opened, then the detail view you are currently opening will open up in the browser.
Make sense?
I suggest you try it out with your hands with your app.
In the meantime, the Appsheet default “share” button is just an Action to “start email” technically. If we wish something different with this action, then my belief is we do not necessarily stick with this default button, but manually construct the same action and behaivior.