Ports aren’t the same as remasters. A remaster means tweaking the actual textures, modifying the renderer etc; not just making sure it works on other platforms. This is much closer to design work.
I looked them up (Sperasoft) and it’s an interesting company. They’re far more than porters or even remaster makers. They’re deeply involved with AAA projects – not remasters, but the actual games (e.g. they’re contributing to the next Assassin’s Creed). They’re essentially contractors/outsourcers to Russia and Poland.