I'd say it sorta feels like a SEGA game if all you think about when it comes to SEGA is Jet Set Radio, and even then that's a bit of a stretch.
I agree, there is no link between something like Shenmue or Jet Set Radio; Panzer Dragoon, Super Monkey Ball, House of the Dead or Daytona... They share almost nothing in common apart from all being developed by SEGA and all being great games.
I think when people say 'this feels like a SEGA game,' what they really mean is; it is invoking a feeling I had once while playing a SEGA game. Which is nice for you, I suppose, but it means nothing to anybody else. What I feel is a SEGA game probably has nothing to do with what you feel is a SEGA game. Considering I have had that feeling with a number of games in the past few years, most of which have been nothing like Splatoon (or Jet Set Radio) but often RPG or action games. I'm going to bet my idea is different to Radrappys'.