Hi meirluc.
Allow me to respond.
The statement in JTM was probably more or less accurate at the time it was written: at least several months before it was published. Maybe getting on for a year..
Remember they had all the shenanigans with the "top journal" (or journals) faffing about asking for amendments and rewrites (at least that's my supposition), before they decided to pay and get it put out in a timely fashion by JTM.
By the time they got to the SNO update, they wouldn't and didn't repeat the statement (as far as I'm aware). Because by then, they would have known it was no longer accurate.
As to why, the superior survival of late entrants occurred, I like 3(a) the most.The other factors you mention may have played their part, but 3(a) was probably the most significant, in my opinion.
Regards.