Is this a decent style or a good way of coding it?
Yes, and probably more readable than nested if statements.
It is assumed or expected that a list will be the second parameter.
With AutoLISP, the arguments order doesn't matter more than make the code more readable (or similar to built-in functions).
For example, most AutoLISP higher order functions (mapcar, vl-some, ...) require the function argument as first argument but
vl-sort take it as last argument.
The choice of arguments order is more important in F# due to the pipelining ability (as List.map or List.exists, List.sortBy or List.sortWith requires the list as last argument).