NOW() function inconsistent between use cases for XDIFF and Value Filter

L2023.3 Release Notes
DateDiff Functions with Now() as a Parameter
A dashboard designer can calculate the difference between a value of a date dimension and the query execution time (according to the Sisense server). Now() can be used as the <end time> parameter in the following formulas: {DateLevel} Difference. See the description of each of these formulas in Dashboard Functions Reference.

It can also be used as the <start time> based on testing though the documentation explicitly only mentions <end time>. However, if you try to populate the function with a <time field> you'll receive a syntax error. The syntax is listed as 

DDiff(NOW(), <start time>)

To use the NOW() function as a value filter
Dashboard Functions Reference #NOW_Function

The syntax is listed as

((<numeric field>), NOW(<time field>))

Attempting to exclude the <time field> results in a formula error. 

We and our clients find it confusing that the <time field> is required in one case and explicitly not allowed in the other.