I have asked about ep13 lock indication and have learned that the gate adjusts to the target when locked. Upon further investigation I found that this feature does not function at all at the moment.
This is how the seeker looked like about a year ago, when it functioned properly:
And this is how it looks now:
There is no gate, just full cross and it never locked or not locked. That explains my previous confusion. I remembered at the back of my mind that there used to be some indication of lock.