That's definitely some weird behavior.  The fact that it happened with a normal paste versus a text-only paste (on the video, at the end when she did Ctrl+V versus Ctrl+Shift+V) does kind of make sense.

When you are doing a regular paste, it is attempting to retain all the formatting, converting all of Word's propritary formatting weirdness to the HTML formatting that LFForms uses.  When doing the Ctrl+Shift+V paste, then you are doing a "Paste as plain text" and it drops all the formatting and just pastes the text.

Something about how it is converting from Word's formatting to the HTML formatting is causing the behavior you are seeing.  I suspect it is a bug with how that Rich Text field handles pasting text that includes formatting, but I can't say for sure.  I know copying formatted text from Word to anywhere else is notoriously finicky.

I wonder if, weird as it sounds, Word is using a character in there that isn't actually a space, and so LFForms is struggling to maintain that value through paste and submission.

I would recommend using the Browser inspector to see if you can identify how the text looks at that deep browser HTML level after it is pasted into the field but before hitting the Save Draft button, and also after hitting the Save Draft button.  You could also examine how the field variable looks on the Monitor page.  Hopefully there is some indication what is going on in the spacing between those words.

Another idea would be to try to examine the text in an editor that can let you see more complex formatting.  I like Notepad++, and it has a bunch of add-ons you can include to do stuff like view the text as Hexidecimal (I had to do that once when Excel kept adding weird hidden characters to the start of a CSV file that was breaking an import process in another program, it wasn't until we pulled it into the Hex view in Notepad++ that we could even see there were extra characters there that never showed when viewed as normal text.

EDIT TO ADD: Actually, my suggestions don't really make a difference.  I went ahead and tried to replicate the behavior, and was able to do so, and I can't see anything about the particular spaces that explain why they are getting lost.  I can see that the text in the field displayed on screen does appear different after the paste before the submission versus after the submission.  But I don't have any explanation why.  It does seem like LFForms is doing something at the submission to clean up that text formatting to be saved, and the issue seems to be happening as part of that behavior.