I should note that, although these plants have big leaves, the reason its probably not mentioned (to address the original question directly) is because its very normal. Bananas are known for having big leaves, and even the photo I showed is not unusual at all. If you ever walk through a germplasm collection in the tropics, and you were asked to describe the varieties, you would see that big leaves quickly becomes something common among countless varieties, sure some are bigger than others, but its not unusual.
The largest leaves I have seen were on a conservatory grown M. itinerans 'Burmese Blue'. They weren't even flowering yet, and there was no way I could measure them directly, but based on the things they were next to I estimate they were about 18ft long and 4-5ft wide. The plant in reference is in the photo below at the Denver Botanic Gardens. It is hard to gauge just how big it is from the photo, but in person it was a very impressive plant and one of the largest Musa I have ever seen up close.
