I can see it, myself. I’ve spent anywhere from six to sixteen hours with Destiny at this point (depending on if we’re counting time spent playing the Beta) and I remember thinking to myself at multiple points that some of Destiny’s design choices at least seemed to inform Halo: Reach’s design. A lot of the Guardians’ powers reminds me of Armor Abilities in Halo: Reach - secret weapons in the back pocket that are on a recharge timer. Of course, Bungie had to find a way to flesh out equipment from Halo 3, but I strongly suspect that Destiny helped inform the route Bungie took.
Some of the environments are so strikingly similar to those found in Halo: Reach, too. One of my first thoughts when looking at some mountains in the distance on the Cosmodrome was that the horizon line seemed so reminiscent of the horizons in Long Night of Solace and/or New Alexandria. Also visually, some of the Guardian armor reminds me of the more exotic pieces of MJOLNIR from Halo: Reach - that camouflage netting on the Scout armor reminds me of the Hunter cloak, Emile’s skull carving reminds me of some of the personality in Destiny’s armor, the extra wrist protection and leg packs are kind of similar to the Hunter’s cloaks, the Titan’s marks, etc. I don’t know which game informed which as far as armor goes.
I also found what I feel is some answer to Bungie’s radical departure from the Ranked and Social partitions from Halo 3 in Halo: Reach through Destiny. The Crucible in Destiny is some of the most pure multiplayer you’re going to get - no ranking system, no Custom Games, no Private Matches, no Forge. Just three gametypes (King of the Hill, Team Deathmatch, and Free-For-All) and a bit of Guardian killing. This definitely reminded me of Halo: Reach’s de-emphasis on the competitive aspect of multiplayer - Bungie doesn’t want people to seriously compete; they just want people to play. It’s less about infrastructure and more about just pure gameplay. It’s a silly design choice for them to have stripped the multiplayer so bare, but the result is that the Crucible feels like a natural extension of Destiny and its lore, instead of the pure spectacle of Halo multiplayer. It makes me wonder if this was informing their decisions in Halo: Reach.
It’s also worth noting what is radically different between Halo: Reach and Destiny. For one thing, Halo: Reach tells a tight, well-paced narrative that focuses on actual characters and emotional cutscenes. There’s a weight to everything in the Campaign. Destiny’s campaign and story have almost no weight. Because of the social aspects of the game, there is no pacing - everything is really fluid and shallow. The plotline is paper thin with almost no real structure or characters. It’s all hazy. So where Destiny went down the more massively multiplayer open story pacing, Halo: Reach was downright classic linear Halo storytelling.
The multiplayer infrastructure was simply much more superior in Halo: Reach, too. Destiny’s grand stall of a whopping three game modes available to play with no Custom Games or Private Matches simply doesn’t hold a candle to the breadth of Halo: Reach’s multiplayer content. From Forge maps to the “fun” gametypes like Halo Ball or Chess, Halo: Reach simply was the peak of infrastructure in Halo multiplayer. So much content was organized and accessible and even creatable so easily. This is completely unlike Destiny.
So while I think Destiny informed some of Halo: Reach’s design decisions to a minor degree, especially after actually playing it, I do think Halo: Reach was still more informed by older Halo games. The structure of the game indicates that - the partitions between each mode, the tight narrative story, the huge amount of multiplayer content, etc.