Whether you add 1 leap or subtract 1 leap, it is reflected in February. As long as it is a leap year, February is 29 days. As long as it is not a leap year, February is 28 days. As for why February was chosen, it is related to the history of this calendar. This calendar originated in the Roman Empire. In ancient Rome, February was the month of executing prisoners every year, so people wanted this month to be shorter, so only February was the shortest. It is also related to Augustus Octavian, the heir of Julius Caesar. Originally 1 October1,3, 5, 7, 9,1day, April 30th, June 8th, 10, 12, February 29th. In order to show his greatness, Augustus Octavian took out February of 1 day and put it in August when he was born, and adjusted the following months accordingly, naming August after Augustus. This is today's calendar.
As for whether we have caught up with "every 100 1 leap, and then every 400 1 leap", 2000 is an integer multiple of 400, which is a leap year, and we have caught up. However, 1900 and 2 100 are not integer multiples of 400, nor are they leap years.