If the targeting is selectable, then it would stand to reason that Professor Crater in "The Man Trap" forced his phaser to deliberately miss Kirk and Spock when he opened fire...
Perhaps once the target has been acquired, it lights up or does something to display to the firer that it has a lock and all they do is fire?
Doesn't Crater use the older WNMHGB phaser? Perhaps that model lacked the self-selecting targeting feature of later models. I don't see anything which might be a screen on that prop...
You're right! He does use the older WNMHGB phaser.
But while looking, we have this gem in the 3rd image on the top row:
(direct link below)
We can see Kirk's Phaser-1 attachment on his Phaser-2 is in the "pop-up" sight position as he fires on Crater
Perhaps the reason why a Phaser-1 is required for the Phaser-2 is that the Phaser-1 is the most expensive and difficult to manufacture part? The "smart" electronics and targeting and phaser energy generator reside in the Phaser-1. The Phaser-2 is just a frame that expands heat dissipation and has a large removable power pack. It would be inline with the idea that the TOS movie phasers also continue use a "core" Phaser-1 in the Phaser-2 units IMHO...