The issue with that study is that lt2 wasnt reported, just tte at 88% vo2 max. With how they define lt1, it is going to overestimate it using 2 minute steps so it would have been beneficial to see the estimate for lt2 using the same protocol.
If you look at the 30 minute bout at 80% of vo2max, even the high lt group was mostly around 2.5 mmol, which could easily be above lt1 for most people, or at least the very top of it if you want to say it is a range from baseline up to 1 mmol above it, assuming their baseline was 1.5, its still on the high side of that threshold. Then 88% vo2 was approximately mlss, so still a fairly normal distance between the two.