If he's set the contrast bias range to a value within the range specified in his datasheet then he's not going to break anything.
Not if the applies "the value" to the "contrast bias" pin BUT he is, in some cases, if he applies it to PIN 3 as you posted
Did he say he's got an Optrex LCD?
did he say he did not?

Have you got a manufacturer in mind, when you say the pinout isn't conventional? I don't know of even one manufacturer, right offhand, who doesn't make LCD's with the "standard" 14-pin signal set. Clearly you must know of at least one.
This is getting ridiculous, you already answered that one yourself "Did he say he's got an Optrex LCD?"

He already indicated what his pin assignments are, so referring to pin 3 as the contrast pin isn't really wrong, now, is it?
Not if it is prefeced by "for this particular LCD panel with this particular pinout" but as a generalization is is WRONG!. What if someone with e.g. an Optrex LCD does the right thing and searches instead of posting your 'advice' and applies it to pin 3

Erik