Please consider, we added the settings Zero and Blank for the default number of Words. Some of our users requested this. Some don’t understand what the excerpt is. They set the field blank unintentionally. Sometimes, PHP also creates some issues with the 0 and Null value. That is the reason we used this default setting.
But, you can still set the Excerpt Off using the value as multiple Zero, like 000 will work for you.
