That is interesting, Trof. I would've thought the higher impact the journal, the MORE scrutiny you'd get about details like primers, since the readership is higher.
Yes and no. The high tier journals you can't just publish in like in any others. You need to have a name (or know someone to have a name or optionaly promise something so cool that the editors will be eager to push it). So, while you publish there, you are a well known leader in the filed, or rising star (or the paper has both) so noone bothers that much about the little details. They go for the cool story, many higher IF journals will reject saying the topic is not interesting enough or doesn't have a novel clear messaage, in other words, not cool. It's not that the data are bad, they just not that sexy to be in their journal.
I repetedly hate people publishing in Nature for using non-HGVS nomenclature for mutations for example. If you want to publish a devilishly difficult gene insertion in Human Mutation, you need to spend week in email correspondence with one of the curators to get even the notation right, because it is such a complicated mess. The journal would refuse to publish without a correct mutation name.
Now Nature? Who cares, it's sexy! (it is, though)
Then I sit with clinical diagnosticians and they ask me, which one is right.. the one by HGVS or the one everyone is using, even that famous paper in Nature.. what can you say?
You would think that top journals need to have a more rigorous control of the data, but they likely more rely on the people-basis than the data itself and more important is how cool the story is. Mostly they are right and the data are correct and cool at the same time. But sometimes, as with the case of the famous arsenic eating bacteria in Science.. it was soo cool and so anticipated, that it blinded them so much to miss the major flaws in the paper, and many objections were found within the second day the paper was out. Those would be caught by some sceptical-style reiewer, but for some reason they were not. Coolness won.