CRUD is an acronym commonly used to exhaust the "manipulation space" of data.
What can you do with data, broadly speaking? It can come in and out of existence (create and destroy), and it can read and write it (read and update). But "writing" data doesn't necessarily refer to a specific bit of data. Overwriting would be capture the idea. The creation of "the data" is the initial write. If it's a single scalar value, for example, the only thing left to do is over write, aka update, the field. If it's a file, then you can expand the data when data is the file. But if data is the individual characters or words or content, then even then they have an initial creation phase (within the file) and an overwriting or updating phase (within the file).
This is similar to the CRUD-like HTTP Request Methods in their alleged exhaustiveness
There are interesting questions here regarding what, in fact, are the MECE verbs that describe what you can do to data?