The old travel manual still applies because reducing the length of a stay to only two weeks does not guarantee low prices in the low season.
Historically, it is not the length of the trip that matters, but planning.
The record shows that other factors, such as local holidays or special events, can double the price even if you reduce the duration.
For example, in Hammamet, even in the tourist low season, if a music festival is announced, hotel prices skyrocket, regardless of whether you stay one or two weeks.
You need to look beyond just the duration to find the really good deals.