I've imported a spreadsheet with 12pt text. When displayed on the page, the text size shows 12pt in the toolbar, yet inspecting the size using dev tools in Chrome shows the text is 9px. Since I have a large monitor, this is quite small.
The problem can be seen by importing the spreadsheet attached to this post I had made last week. The problem is visible in the spreadsheet impot/export demo as well.
Now that I'm looking at the demo, I also notice that, while the toolbar shows "12" (and an Excel user would assume that means 12 point), the text there is 12px which, again on my large monitor, is much smaller than 12 pt.