3月なのに February update（2月のアップデート）だったので、内容を Diff ってみたのですが、余計な半角スペースをとるなどの細かい修正でした。機能面での変化はないようですね。
Enhanced digital writing assistance
Note: This feature is only available to Office 365 subscribers who have joined the Office Insider program. If you are an Office 365 subscriber, make sure you have the latest version of Office. These enhanced style suggestions are available only when your proofing language is set to English.
Editor, your digital writing assistance has now more style suggestions to offer. Editor checks for potential writing and style issues and indicates the word or phrase with a dotted gold underline. When you see a gold dotted line below a word, right click on the word or phrase and consider one of the alternative suggestions to correct the writing style issue. For more information see, Select grammar and writing style options.
Move pages from side to side
Open your favorite Word document and flip through the pages by sliding them side by side like a stack of paper. To try, go to theView tab and chooseSide to Side. Your document opens in two page mode. Flip through the pages using the backward scroll on your mouse wheel or use the horizontal scroll bar to move through the pages. Also, you can chooseThumbnails when you haveSide to Side selected, to see your entire document in one view. To learn more, see View pages side to side in a document.
Easier background removal
We've made it easier to remove and edit the background of a picture. Word automatically detects the general background area; you no longer have to draw a rectangle around the foreground of your picture. The pencil for marking areas to keep or remove can now draw free-form lines, rather than being limited to straight lines. For more information see, Remove the background of a picture.