SEARCH function returns array if first argument is array--Huh?

In answering another thread, I discovered that function SEARCH appears to return a sort of an array. This appears to be undocumented behavior for this function. Look at column K in the attached file.

Stranger yet, when the same formula is used for conditional formatting, it appears to iterate through the entire range for a match in the second argument. Also illustrated in attached. Normally, when a function specification calls for a single value as an argument, using a range will cause only the first item in the range to be used as the argument.

Is this intended behavior or a side effect of how Excel is built? It certainly is not evident in Microsoft's Help page on SEARCH. Do you have an explanation of this that is sufficiently rigorous to be able to use this feature predictably?