The point is, the max cabin delta P on the 787 is higher than the 777. So, if champair suggests they pressurize to the max delta P, at say 32k, the 787 will still have a lower cabin pressure altitude (high cabin pressure) than a 777 (or most aircraft for that matter, since 8k has long been something of an industry standard). Hence the comment 'max out at 8k for the 777 vs. 6k for the 787 (again, those numbers are from memory and 787 might be a bit off).
Most people will find that a lower cabin pressure altitude leaves them less drained, as there is more breathable air (and hence more O2).