I know that N.alata produces upper pitchers (I have one).
There are two things to consider here. the first thing
to consider is that a carnivorous plant will always give
up its carnivory if it is in nutrient rich soil or if
it is in stress.
The second thing to consider is that it is often difficult
to get a Nepenthes to produce upper pitcher in captivity.
Usually, you need extreme humidity and extreme light to
get a Nepenthes to produce upper pitchers.
Chris