Yes it can be closer. Its more of a suggestion that an rule to be 22-24" from the bottom of the coal basket to the grate.
Here is a math problem based on my main UDS:
The drum is 34" tall with a Weber lid on top. My top rack is 2" down from the top and the bottom rack is 6" down from that. My charcoal basket sits 2" above a pizza pan that acts as a ash tray. The sides of the basket are 12" tall. So, if the basket is full of charcoal, how close is the charcoal to the bottom rack?
Answer: 12"
My basket is rarely full as that is more charcoal than any burn would ever need. The point is that even though I do have the 24" from the bottom of the basket to the first grate, the fire is most often much closer.