Randy thats also true for any number of trans, including the top loaders. When you 'disengage' the clutch the trans gears, all though now diconnected from the flywheel, continue to 'free spin' (momentum) for a short while. First gear is the largest gear in the trans and has more friction than the other gears when engaging it. By shifting into second first (which always requires less effort on the synchros than first gear) you stop the spinning gears (or substantially slow them down), making the shift into first easier. Sometimes I don't actually shift into second, I simply pull the gear shift back and put a little 'pressure' on second gear to slow or stop the gears from spinning, then shift into first.
With a PERFECT trans with PERFECT synchros the problem is less pronounced when shifting into first, but even then it's not a bad idea to 'bump' second gear slightly first to slow rotation and ease the pressure on the first gear synchros. You can 'feel' when the first gear synchro is showing it's age by the fact that it takes a little more pressure than it used to to slip into gear while rolling. When you 'feel' that over time, it's time to start thinking about learning to 'double clutch' and 'save the synchro'!
When downshifting into first while rolling, like coming up to a stop sign or whatever, I often 'double clutch' just to ease the pressure on the synchros for first. First gear is typically the FIRST gear to experience syncho damage over the life of the trans.
This basic principle, subtle as it is, is a classic example of why some race drivers experience more 'failures' of equipement during a race than other drivers do. It's the 'little things' that tend to save the 'parts' over the course of a race as opposed to 'forcing' things into place. Could be 'little things' like how you use the brakes, manage the rpm of the engine, downshift for the corners, etc. It's a driver trying to 'save' the car for the full race sort of thing.