But the fourth gen is completely different form whatever we are in now. It was just a short one.
What exactly is completely different...? If you're talking about the state of the magazine as a whole, sure, but the manga being published aren't particularly distinct compared to recent years. The only difference is the lack of hits, which isn't that unusual.
I mean of the eight current series he listed, three of them are by veterans and keep a pretty similar style to their previous works. I wouldn't see what makes AssClass and Sket Dance "third-generation" but TES and WW "fifth-generation", if that's how you're defining it. I see even less difference between Yuuna and AyaTri, and the only thing they have in common is genre.
There's also the fact that three of those eight are also less than twenty chapters each, so it feels a little premature to make any judgments about whether they're "completely different" or not.
I mean, when Nura, Sket Dance, and To Love-Ru are in the same generation as Naruto, Bobobo, and Ichigo 100% but grouping Chainsaw Man and Sakamoto Days is where you the line gets drawn then idk what to say. Like I said, if you're just talking about the broad state of the magazine then it makes sense (the situation has obviously changed from 3-4 years ago), but I really don't think "generation" is the appropriate term in that case.