14/2 wire at ends of long run
15A breaker, 14/2 is fine. Likely would be fine the whole way, but 12/2 is also fine, perhaps someone was overly concerned with voltage drop. Voltage drop is much less of an issue if you are using modern lightbulbs that draw much less power. If you love paying the power company to run your big-ol incandescent bulbs, voltage drop would be SLIGHTLY less with 12Ga than with 14Ga over that sort of distance.
So, if you had 1,440W of lights (12A, as much as you should have on a 15A lighting circuit since lights are a continuous load) all at the far end of one 65 foot cable, in the 14Ga case you have 115.9 Volts and in the 12Ga case you have 117.4 Volts, assuming you started with 120V at the breaker. A volt and a half difference - pretty much irrelevant.
In the actual case you probably have of smaller lighting loads supplied by different cables carrying less current, the differences would be even less.