[SiempreViernes]

One of the objections against the improvement observed that is mentioned in tfa is precisely that you can get "trips" from general anaesthesia:

'Schenberg points out that people often report dreamlike and visual, auditory, and affective experiences under anesthesia. “Maybe people who had dreamlike experiences during the anesthesia had more improvement than the people who didn’t,” he says.'

So maybe the trip does indeed help, but evidently it is not necessary to be able to remember if you had one to get the reported benefits.