This is wrong. The behavior of a "normal", "low latency" and "preempt-RT" kernel are all different, and for realtime audio work, the correct behavior is only going to happen with a "preempt-RT" kernel.

However ...

The behavior of the normal and "low latency" kernels have changed over the years too, and on *some* systems (from a hardware perspective), they will function similarly enough to a "preempt-RT" kernel that a realtime audio workflow will be just fine. In addition, the "behavior" gap between a "preempt-RT" kernel and a normal kernel will be less and less apparent as the latency settings (buffer/period size) become more relaxed (i.e. grow larger).

How do you know which systems this is true for? You just have to try it. It is a complicated mixture of many different aspects of the hardware. There's an overview of the kinds of things that can contribute to the need for a "preempt-RT" kernel here: