Umm, not entirely true!
Newly just released phones, maybe........ My son has an S7 that has not been updated in months as far as the monthly security patches go.. The OS update itself? LOL
Correct me if I'm wrong - but yeah, I think Android's monthly updates started with the 8 and 9? (Note 8 also). Up until then yeah, updates were far and few between. I have Samsung Tablets that haven't seen an update since the day I bought them and my Note 3 got 2 updates the 2+ years I had it. Android had a bad history with updates - I think they've finally corrected that just recently though.