Disclaimer: I have no inside knowledge so the rest is pure speculation:
Judging from this tweet by Erik Hansen of Classy Llama (the team that built the RWD features for CE1.9+) and the fact that Rob Tull (also from CL) is pinging Ben Marks (the Magento Community Manager) I would guess the following:
- It was a 1.9+ feature that was slated for launch but was omitted due to time, budget, or both
- The file was left there accidentally and was not caught prior to the production package
- OR: perhaps it is a future feature that will land in 1.9.1 in the fall and this feature is actively being developed
- OR: it was a feature meant for EE-only and was removed for some reason, perhaps to reduce the amount of feature carryover required for M2? (now I'm really reaching)
Less likely is that it was a CL internal project that wasn't ever work contracted for the RWD build but somehow made it into the deliverables. I can't see this happening, though, and the fact that Ben got roped into the conversation on Twitter is probably telling that this was a possible CE core feature that was stripped from the final release.
On a side note - it's not surprising that swatches got removed if they were going to be a core feature. Configurable product swatching is actually quite difficult to implement (I haven't seen anyone do it correctly, FWIW, including myself) and will usually negatively impact performance.
Lastly, there are many community vendors with modules available that do this and I'm sure Magento would take some heat for 'eating their lunch' if they stepped into the space of this trivial feature. Not that they haven't ever done that before, ever.