That's not correct. It depends on the batteries.
If we look at the very popular 14500,
one standard 14500 running a real Joye 510 can't really keep up with the current the Joye wants to pull for peak performance. It
kinda works, but the 14500 is being stressed. The max discharge rating of the 14500 is being exceeded. A LR atty real beats up one 14500. The safety purists would call this unsafe (it does shorten the batts' longevity). The performance purists will notice the same atty works better on an 18650 (most can easily supply 2.5A).
For Joye 510 and LR atty users A pair of 14500's in parallel will not only last longer (vape time), but vape better and safer. Your batts should also last longer (more charge cycles before they start losing capacity).