It probably made sense back when development of the game was greenlit, even if it didn’t make sense when it finally released- back when this generation of consoles was still on the horizon, a lot of major publishers hedged their bets by also commissioning last gen PS3 and Xbox 360 versions of their games. The idea was that if the newer consoles failed to take off, or if sales were lower than expected, then the massive install bases of the Xbox 360 and PS3 would cushion the blow, and lead to some return on the investment.
Of course, that turned out to be unnecessary, and the PS4 and Xbox One broke records with their sales. The fact was reflected in most major games of this year dropping PS3 and Xbox 360 SKUs, and instead opting to focus only on the PS4/Xbox One spec. Not Konami, however. Konami firmly wanted a version of Metal Gear Solid V for the Xbox 360 and PS3, according to a talk by former Konami Technology Director Julien Merceron, as reported by DualShockers. This led to all sorts of issues in trying to get a current gen game to run on consoles with ten year old hardware.
In the end, the development team at Kojima Productions ended up applying two tricks, one on the engine end and one on the toolset end, to make the game transition to the Xbox 360 and PS3. On the engine side, the team stored animations in the consoles’ GPU- this would prevent the need for compression, which would degrade their quality. A lot of developers don’t actually do this, since constant transfers to and from the GPU are unfeasible. But the folks at Kojima Productions ran calculations to figure out if they could make it work with the transfer rates, and implemented a system which allowed to have a small storage in local memory, but most of the animations were still on the GPU.
On the toolset end, the solution was simpler conceptually, though it required a lot of work to implement too- instead of simply compressing the animations and then loading them into the game directly, the development team added a new intermediate step, so that the animation would be created, compression would be applied, and the compressed animation that came out would still be something that could be corrected before being loaded into the game.
Tricks like these are why Kojima Productions used to be regarded as masters of their craft. They really were tech wizards. Hopefully the new Kojima Productions can continue to live up to that pedigree too.