well that’s my understanding of it but this says the WHO ‘recommends’ it’s only given to those who have had dengue before. So maybe you did have it if they broke protocol.
I had less than 8 years when I bought it- my logic was: the retirement visa rules change all the time and I’m sick of justifying my life every 12 months. And, one of the 20 year options is the same price as the 10 year - minus some perks (hence the cheap price). No regrets so far I love it.