VFSUX won't work since the initial minimum is too high. Try VFSTX which is the investor share version. I used this until I wanted more risk and started to use VCSH instead.
If you are one of those folks who when they lose their job in February want to withdraw all their future March to December expenses the next day and put them in their checking account, then a short-term bond fund may not be for you. If you want to withdraw gradually as you need to pay expenses, then a short-term bond fund could work.
Here is an important difference between ETF's and mutual funds: The settlement date. For ETFs, if you sell, you cannot move the proceeds to checking until 3 days later because settlement is T+3. With a mutual fund, settlement is T+1, so you can move the money to checking the next day.
It's all about market timing, uh, I mean rebalancing, uh, I mean opportunistic rebalancing, uh, I mean short-term opportunistic rebalancing due to a short-term change in one's asset allocation.