No, it makes perfect sense to me.
I wouldn't be worried about it at all. Brad has mentioned many times in post game press conferences that our defensive system is based on switching, and that in turn leads to points for guards or shooters.
Sexton/LeVert were beating bigs off the dribble, and LeVert was feasting on Smart. But Smart generally isn't the greatest at shutting down speedy guards with quick first steps. He's really good at forcing them to take tough shots or deliberately force a turnover.
Ultimately, most of the games where players would score 30+ against us, 60% of the time they are taking tough contested shots, which I'm 100% okay with. Now our defense game plans around forcing guards or other players to take inefficient shots, like mid range, or step back tough fadeaways, (Sexton took like 7 of these, and made at least most of them) but again, as I said before, I'm 100% okay with that.
In today's league with all the rules and hand-checking, anyone that has a decent jumpshot, and ability to play PnR can probably get at least 15-20 PPG. I'm talking about decent, not like players with high ceiling or potential or MVP caliber like Harden/Westbrook. I mean January was one of our worst defensive months statistically, because we didn't trust each other, and kept helping out instead of forcing tough shots/closing on shooters. We gave up a lot of wide open kick outs and open layups. So I trust Brad will make the right adjustments in the playoffs.
EDIT: Don't let the Brooklyn Nets fool you into thinking our defense wasn't good. We were missing key players, and Tatum, (one of our best elite defenders,) was out of the game. The Nets got smoked last night by the Grizzlies. And we were just fresh off on a b2b.
We're still ranked 4th in defensive rating.