Bungie engineer Roger Wolfson explained that it decided to cordon off new-gen from last-gen players for gameplay reasons and not due to technical limitations.
“I’ll speak for the hypothetical player,” Wolfson said. “[On PS3], I have a disadvantage sniping across the map because [my opponent with a new-gen console] is only two pixels on my screen, and I’m four pixels on his. You see that in the world of PC gaming, where people are always racing to the best video card to give themselves the advantage.”