That is correct.
They correctly note that geologists do say that some adjacent layers are millions of years apart. What creationists then ignore is the "some adjacent layers" part. They claim that geologists think ALL adjacent layers are millions of years apart, which is silly in the extreme. Once you take that part of their argument away, the rest just falls apart.
They also like to confuse how long something takes to form and how old it is. They will claim that since layers can form quickly then it means they are young. When you think about it, you realize how wrong they are. A building I work next to only took about 6 months to build. However, it is over 100 years old. For some reason, creationists think those two statements are in conflict.
So yes, the adjacent layers surrounding a polystrate tree can form relatively quickly, but that doesn't indicate that they are young. With these two basic pieces of logic in place, the polystrate fossil argument is completely refuted.