A block like this appeared during the development of Scratch 2.0, called “all at once” or “warp speed”. It appeared in the control blocks. I'm not exactly sure why it was removed, though it was made up for by adding a “Run without screen refresh” checkbox onto custom blocks. While the workaround of putting scripts in custom blocks can work if used sparingly, it may become messy if you make a project involving many of them.
As for possible New Scratcher confusion, the checkbox in custom blocks isn't exactly explained as well. However, looking at the Scratch Wiki could help, or asking a question in the forums about it. There are probably other blocks that can be confusing to other New Scratchers, like this block.
(() mod ())
In short, I support adding the block back.