I get the "unenthusiastic" point, but at the very beginning of when he gets into his impressions of the sound, he says that the whole video review is going to be fairly short because usually he spends time focusing on problems or negatives, even if they are very minor - but here he has no negatives to report. So he's saying the review is unusually short and straightforward because he literally has nothing bad to say about them, not even a nitpick.
What surprised me most is that he said their dispersion is exactly perfect for what he likes. For some reason, I've always been under the impression that Genelec Ones dispersion is on the moderate side (not overly narrow, not exceptionally wide), while Erin tends to prefer wider dispersion speakers. But I also noted that he characterized their horizontal beamwidth as +/-60 degrees, whereas Amir's review shows an almost identical measurement but Amir characterized it as +/-50 degrees and called it slightly narrow.
As to the GLM question, I have to agree with Erin here. I would never use my Genelecs without GLM, and personally I agree it's silly for anyone who drops the money on them NOT to use GLM. But all the other speakers Erin reviews, he evaluates without any room correction (or phase correction). So for consistency it makes sense that he did the same here.
Finally, I found it fascinating that he mentioned a very slight directivity increase around 2-3kHz, which has little to no effect in the near field but which shows up as a slight elevation in the estimated far field in-room response. He's not the first to observe something like this, but nevertheless I found it interesting because it explains that mysterious "zinginess" that some folks sometimes say they hear in that range with Genelec Ones.