It's a common remark because many bad batteries with supposedly high capacity but actually abysmal performance are branded, or used to be branded, fire-something. Trustfire being the most famous brand.
Basically, most cheap batteries claiming huge milliampere capacity, will only give that capacity if discharged at very low amps.
Put them on a vaporizer, and they will discharge in no time at all, as the amp draw is pretty high, and give you a wimpy vape.
In general, it's safe to go for tested batteries.
Seynybor and efest are cheapish batteries with good performance. Torchythebatteryboy on ebay is quite famed for testing batteries and pubblishing results.
I can confirm his torchy 18350 are better than AW and cost much less, for instance.
