Did Gran Turismo ever have a "real career mode"?
Wait, so it requires the connection because they're worried about people cheating in the single player portion of the game. Am I reading this right? If we don't have PS+ we can't go online. So than the check is meaningless.
You don't need PS+ to go online, or to connect online in games for that matter.
Take Nioh for example. You could still access online features in the game without PS+, like the graves of other players who died, or the teahouse weekly online clan rankings.
It's just that the online multiplayer features are manually locked behind the PS+ paywall. But if a game requires you to do something specific online during single player modes, they won't require PS+ for that.
There have even been games that let you play online multiplayer without PS+ on occasion. (Some Beta tests)