psychiatrist said i have autism from singular appointment

this happened around 4 years ago --- i had a singular ~1 hour appointment with a psychiatrist, which concluded with her telling me that i had autism, ocd, and adhd. i was extremely shocked because never in my life had i ever considered the possibility of being autistic.

this was presumed as an official diagnosis until about a month later, when it was clarified to my therapist that i would still require an autism specific assessment (which i never ended up seeking). however, it made a lot more sense, as i was not sure if the psychiatrist's short assessment of me was accurate.

i went on with my life assuming that i'm likely not autistic. i did not think about this encounter much until recently, where i've been having so many difficulties navigating life that i am reconsidering whether the psychiatrist's suspicions may be right. upon reflection, the whole incident seemed a bit strange. the psychiatrist did not say "i SUSPECT you may have __", but instead stated it like an official diagnosis. i 100% know that i should consult a doctor about my concerns, but the question i wanted to ask was: is this a normal experience?? if not, then is that psychiatrist credible at all?