I see quite a few FL2s in ads with oddly cut passenger side dash. Does this imply airbag deployment / replacement?

Photo for reference.

I don't think any came like this from the factory.

https://ibb.co/Pv3mK9pt

Nope. IMO normal.

Almost all the better condition ones seem to have no lines there ... what are they accessing if not the airbag?

I've had my car from new and there is a distinct outline there but the lines are not cut. driving on the right side

It's just the effect of strong sunlight through the windscreen over time on the plastic.