I'm no medical doctor but that definitely isn't true lol. Ejaculating within a few seconds after insertion is definitely classified as premature ejaculation if you ask any Men's health doctor.
If I were to cite some famous peer reviewed published research on the topic:
"The overall median value was 5.4 minutes"
Waldinger, M.D., Quinn, P., Dilleen, M., Mundayat, R., Schweizer, D.H., Boolell, M. (2005)
A multinational population survey of intravaginal ejaculation latency time
https://pubmed.ncbi.nlm.nih.gov/16422843/
"Measured on a stopwatch, it takes an average of 5 to 7 minutes for a man to reach orgasm and ejaculate. But the overall range is wide, from less than one minute to over half an hour."
Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); (2006)
https://www.ncbi.nlm.nih.gov/books/NBK547548/
So yes, if you ejaculate in less than one minute - it's definitely premature ejaculation and you might want to consult a Men's health medical doctor for the options available to try and treat it. You could also leave it as it is, but enjoyment during sex would probably be short lived compared to the average male.