That certainly is odd. The SAV files are purely there to save your game data. You do not need to open them.
Viewing post in The Second Circle: A HellTaker Fan Game comments
A small tid-bit for you unless you already figured it out from all reports you got.
The engine you use saves everything in .sav files and happy coinsedence that this is the same formatting which is used in Titanfall 2 and L4D-s. I am not sure if tyrano allows to change that at all but I guess you can just create a folder named save data and drop stuff in it near the game.exe to avoid confusion.