I don't like to doubt Jason, but this is still one of those rumors that seems so strange to me. I can think of one good reason for it to happen, but definitely more for why it doesn't make much sense...
Reasons It Could Happen:
1) Both Horizon: Zero Dawn and Death Stranding run on the Decima Engine. Kojima Productions made a lot of enhancements to the Decima Engine on their work with Death Stranding, and shared all of those improvements back to the engine's creator Guerrilla Games. Those improvements would include building-in native support for a PC port - so from a technology standpoint, Kojima Productions has already done most of the legwork for Guerrilla Games to port Horizon over to the PC platform.
Reasons Why It Won't Happen:
1) All that being said, Kojima Productions is a WHOLLY INDEPENDENT studio - they are NOT owned by Sony. Sony is simply the exclusive console publisher for Death Stranding. The Death Stranding IP and game are wholly owned by Kojima Productions, and of course they can do with it what they want. And it was always in the plan, from day one, for Death Stranding to come to the PC as well as the PS4.
2) Guerilla Games IS owned by Sony. They are what you call a first-party studio. They cannot simply port their game to PC, unless Sony asked them to...
3) ... which brings me to why would Sony ask them to. Even with Kojima dong the heavy lifting on getting it running on the DX12 API, different Intel/AMD processors, etc., it would still take some engineering work for Guerrilla and why would they put that time/effort into getting a 3-year old PS4 game out on the PC now? Unless as others suggested, and Sony plans to do this for all games going forward, I just don't understand the business sense in it.