Indeed, there is more. As they develope a "daily" snapshot as it is so called, they test it first and if it doesn't work out, they retire the number and save the file as an archive and move on to the next. They don't release a daily firmware if it fails to do something they were working on. No sense making it available if it isn't any better. Therefore, the 0.9.5209 is proabably identical to 0.9.5020 with the youtube fix. All the missing version numbers in between were probably deemed not worthy to present to the public.
This is the most common way of doing it and makes perfect sense.
Re-writing over one that did not work properly may cause more problems down the line so you begin anew from the last good starting point and rename the file to a higher version. The missing ones you end up seeing in-between the releases are usually the ones that had some flaw or defect and were not worthy enough to put out to the public.