I think @MrWookie covered it upthread, but the optimal strategy in hard mode is very different from easy mode, imo. You have to be careful not to get too locked in too early.
This assumes that your goal is to never fail in 6 even if you take longer to get there on average. This is my goal, but it seems like a lot of people really want to get it as early as possible.
If I played Wordle 1000 times, I’d consider 1000 6s a better result than 999 3s and one failure to complete in 6. But that’s just me, I suppose.
In hard mode, if you try “light” and get _IGHT, are you basically screwed and forced to just guess tight, might, sight, fight, etc. until one of them happens to work?