For the 737NG, it appears that using 10 minute take-off thrust time limit compared against extended second segment with 5 minutes thrust gives the same limiting performance weight
I have no ops background with the NG but I can't see there being all that much difference at the coalface between the NG and other twins. I suspect that your statement is taken selectively out of context. The differences will be seen particularly for later obstacle considerations .. are you just looking, say, at first/second segment problems ?
Are you able to provide some AFM evidence to support your statement and then we can, perhaps, offer a comment or two ?
Could it be to do with the requirement to have 1.2% gradient capability above 400ftAAL?
Perhaps it's just a slow start morning for me .. but which particular requirement are you citing here ?