First of all Dissociation is not a form of psychosis.
Dissociation is similar, but different to psychosis, however they can often be confused for each other.
Someone going through a dissociative episode may be thought to be having a psychotic episode, and in some cases, dissociation may be the initial phase to having a psychotic episode.
The difference between the two is that, while dissociation causes a disconnection from reality (i.e., loss of memory and sense of identity), psychosis causes some kind of additional experience (i.e. seeing and hearing things that don’t exist) (MedicineNet, 2022).
When you look at my answer to What is dissociation? that can also be confusing, as dissociation can involve seeing and hearing things which are not there (in a dream-like state). But, in psychotic episodes, you are not in a dream-like state.
[Psychosis] occurs when there’s a disruption in your thoughts that makes you unable to tell the difference between what's real and what isn’t (MedicineNet, 2022).
With dissociation, you know you are disconnecting from yourself, and therefore you know that your dissociative state is not a real state.
So, to your question,
Are people suffering from a dissociation episody often psychotic aswell?
The simple answer to your question is "No, not necessarily". The APA Dictionary points out that dissociation can be a psychological defence mechanism, so, you can be just as dissociative and be mentally healthy prior to the dissociation as you can be dissociating while having a psychotic mental health condition, or taking dissociative drugs.
References
MedicineNet. (2022). Is Dissociation a Form of Psychosis? https://www.medicinenet.com/is_dissociation_a_form_of_psychosis/article.htm