Assuming one has Word open, then if you use "Copy" when copying from another application the copy goes into the operating system's clipboard (the Windows clipboard if using Windows). If one uses "Copy to Clipboard" the copy goes into the Office Clipboard. You can see this if you have the Office Clipboard viewer visible in Word and try the two copying options. In one case the copy appears on the Office Clipboard and in the other case it does not.
The two clipboards have different behaviours and that probably accounts for the difference you experienced.
Yours is an interesting observation worth remembering when encountering 2 columns
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