It is not *required* to do mass-updating, you can change each product one by one if that is your cup of tea, but for those who are competent enough it is an additional feature that helps save a lot of time.
We have lots of customers using it successfully and without any issues for years.
This is because in QuickUpdate mass editing / mass updating is a two-step process - that is - you first make all the changes in the interface and and when you are ok with them, you "update" the changes in the store; until then you can "undo" any changes you made (as shown at the end of the demo below). This way you are way less prone to making unwanted or problematic changes.
Attached demo, of single product and mass-update for visibility: