In the Definition Query window in SQL mode:
When typing the word “when “, it autocompletes to “WHENEVER”.
I don't know what use case WHENEVER applies to, but 99.999% of the time we'd want WHEN, not WHENEVER.
Example:
I typed "field1 = case when ". Note the space at the end of "when ".

It autocompleted "when " to "WHENEVER".

That's not what I wanted. It changed valid SQL to invalid SQL.
ArcGIS Pro 2.6.8.
Related: Optionally disable SQL expression autocomplete