This is definitely not a Snarry. Ever since last year we've had the intrusion of fics like these in Snarry games and no matter the mods, this does not belong here. The Mentor genre never was a Snarry and never will be.
Apart from that, I read because I love Severus mentors Harry stories but we don't even have that to be honest. We have very little Severus and Harry interaction at all, it is mostly a Severus centered fic. Harry is more of a side story, an after thought.
Disregarding the games, and all, I loved it. It was well written, and I love Severus centered fiction so I enjoyed this take on it very much. I love Fili here as you gave him a dimension lacking so often so it was a pleasure to read. The OCs were not overpowering as they often are in fics, and I thought them really well done; it is difficult to find the balance for most authors.
Anyway, I did enjoy it very much; just don't feel it belongs so to say here at all.