I was running errands in town with my V1 in L mode, when I came to a stoplight where there were X and K door openers behind me. The V1 alerted to the openers, then stopped when I got to the light. I thought to myself, it should still be picking them up, they aren't that far away. So I switched V1 to A mode, and lo and behold, several bogeys on both X and K appeared. Switched back to L mode, bogeys gone. Back to A again, bogeys back.
So, at least as far back as 3.813 (pre-POP 1.8 V1), there has been K band filtering in L mode, and probably small-L mode as well.