if that is true disks should come with a very visible note stating this... seriously, 3 months would be nothing. i doubt it is true because 3 months is a time frame which should be surpassed quite often making this more known.
Outside of that narrow scenario, the three months figure is wildly wrong and should not be repeated. Lower temperatures, a consumer drive, and not having used up 100% of the write endurance will all drastically lengthen data retention.
(However, under no circumstances should you trust a cheap USB thumb drive to retain your data. Those tend to use lower-grade flash memory and lower-quality controllers. If you need an external device to reliably cart around data, shop for a "portable SSD", not a "USB flash drive".)
> It depends on the how much the flash has been used (P/E cycle used), type of flash, and storage temperature. In MLC and SLC, this can be as low as 3 months and best case can be more than 10 years. The retention is highly dependent on temperature and workload.
Are there any modern sources provide more accurate stats? "3 months to 10 years" is so vague as to be useless.
To achieve that target, when they are new they must have a retention time of a few years, but you should better not count on that.