There is nothing wrong with the entry you used but sometimes WK leaves out some definitions/meanings mostly in verbs that have several meanings (the meaning “omission” comes as fifth meaning in one of the monolingual dictionaries I looked up: ㊄省く。「手を抜く」
「朝食を抜く」) but the system is designed so you can your own definitions. For sure, the should have a better example sentence that reflects the meaning that is being taught.
It’s more that I would say this example sentence is not such a helpful one for the verb 抜く, since even in a monolingual dictionary 抜き as a suffix has its own entry.