What Cross-Progression Actually Requires Behind the Scenes
Letting a save file follow a player from console to PC looks like a small feature on a box, but it requires an entire account and data-syncing system most single-platform games never need to build.
The existing piece on cross-platform play and console exclusives in this category covers letting players on different platforms play together in the same match. Cross-progression is a separate feature entirely, easy to confuse with it: letting one player's actual progress -- save data, unlocked items, currency, achievements -- follow them across platforms, whether or not they're ever playing alongside anyone else at all.
The foundational requirement is an account system that exists independently of any single platform's own identity system -- a PlayStation account and a Steam account have no built-in relationship to each other at all, so a game supporting cross-progression has to layer its own account on top of both, and every other supported platform, and have players explicitly link each platform's login to that one shared account, before any progress can actually sync between them.
Once accounts are linked, the actual save data itself has to live somewhere platform-independent -- typically a cloud save service the studio operates or licenses -- rather than staying local to whichever platform's storage it was originally written to, since a locally-stored PlayStation save has no way to reach a PC. That server-side requirement also creates a genuinely tricky edge case: a player who already has separate, divergent progress on two platforms before ever linking them needs some conflict-resolution rule -- keep the higher-progress save, merge specific elements, or force a manual choice -- rather than one save simply overwriting the other by default.
Purchased content adds a further wrinkle beyond save data alone: an item bought through one platform's storefront was purchased under that storefront's own terms and doesn't automatically exist as an entitlement on a different platform's storefront, which is a genuinely separate technical and contractual problem from syncing progress -- some games solve it by keeping cosmetics tied to the shared account rather than any one storefront, but that requires deliberate design up front, not something that falls out of cross-progression support automatically.
None of this is impossible -- plenty of live-service games ship exactly this system successfully -- but it's a real, ongoing infrastructure commitment layered on top of whatever the game itself needs, which is why cross-progression support tends to correlate with larger, live-service-style titles built with this system planned in from early development, rather than bolted onto a smaller game after the fact.