Does making class final help compile time be faster?

Yes, it does. Apple has given specific guidance in this regard.

As you yourself say:

making class final helps only optimize Swift Method Dispatch.

Yes, so if this class has no subclasses, the compiler will make that optimization. But if a class is not explicitly marked as final, the compiler has to look for subclasses in every other file, because their existence changes how the details for this class are compiled (i.e. in order to make that optimization). And that search adds time and overhead.

So if you know that your class has no subclasses, always mark it final. On a large project in the real world, the difference is very noticeable.