I know that the Taskbar is a Windows issue.
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But the way Office applications start and run is entirely an Office Issue. I want to know why Office 2010 and 365 work differently on the taskbar.
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I've had too many cases when a file causes an application crash. If I have multiple files open in the same session, all of the documents are lost. Hence work is lost (regardless of the save options (and no I prefer not to use OneDrive) ). So I prefer to open documents and spreadsheets in separate windows sessions.
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When I pin an Office 2010 tile to the taskbar, I can open the application separate Windows sessions.
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When I pin an Office 2016 tile to the taskbar, the shortcut always uses the same session. Using the <WIN><#> shortcut or clicking on the tile just toggles display of the application window.

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Both applications have a startup parameter that will start the application in a separate session (/x for Excel and /w for Word). When I use a shortcut on the desktop or use the Run dialog with these parameters, both Word and Excel 365 start in separate Windows sessions.

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Even if I put the parameter in the taskbar tile, the taskbar always only works with a single windows session.

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Eh?!

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Why do 365 tiles/shortcuts on the taskbar work differently than the run dialog and desktop shortcuts.

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Is there any way to beat the taskbar into submission? Another parameter?