Why is it a bass singer can singer high falsetto than the baritone singer?

That statement has the potential to be true and false. Once vocal fach doesn't determine how much of a range they have. You have to look at this from an individual standpoint. All instruments are different, even if the same individuals share the same vocal fach.

For example, you can have a Soprano who has a lower range than a Mezzo, and vs versa. There are Mezzos that have a higher range than Sopranos. This is why we have to be careful talking about vocal fach and range. Vocal fach isn't determined by one's range, it is where the voice is most comfortable while singing. So perhaps the particular bass you are discussing just has a wider range the the baritone you are discussing. This could go the other way around.

Whenever you discuss falsetto, take vocal fach out of the picture, and look at the range of the voice itself. You will find people's ranges and octaves differ from one individual to the next. So you will likely find a baritone who indeed as a higher falsetto than a bass (which is more likely in many cases). But to answer your question in general, one's voice part doesn't influence one's range. If that were the case, I would be classified as a Soprano, because my range can go beyond a High C. So, look at the individual, not the vocal fach. Range and vocal Fach are two different animals. And don't feel awkward for not knowing. Many people are confused about that also. Thanks for asking such a good question.

try singing falsetto starting low and go high. Notice that your voice box moves down? The lower you can go with your voicebox the lower you can sing, but when you're singing falsetto it's basically reversed.

A bass singer has longer vocal chords and thus has a greater potential voice range. With training, this potential can be realized. You have likely heard this phenomena using highly trained voices. I sing bass and baritone in my natural range, but can do a very credible Mickey Mouse voice and sing along with the Four Seasons, but I'm not in the Lou Christie ("Lightning Strikes Again") range by any means.