I've always seen PPC as a PoS currency, I haven't followed it for some time now and forgive my ignorance on this issue, based on what I've read I would like to know since when did it become PoW too (if it did)?
PPC is not just a PoS currency, it's where PoS was invented in the first place. But it's always had PoW as well.
In a pure PoS currency, initial coin distribution is a problem, and generally it needs a centralized authority that decides how the initial coins are given out. For example, the authority can be a company that sells the coins, which goes against everything in the original ideas of cryptocurrencies. So PPC used PoW to ensure that anyone can mine the initial coins in the same way as in Bitcoin, but the PoW block reward was designed to get smaller so that PoS would dominate in the long run.