If applying based on having had a greencard for 5 years: If you have a long absence that disrupts your continuity of residence, and BUT FOR that long trip you could apply for naturalization, the long absence does not make you start counting over from scratch.
This only applies if you have a long absence that broke the continuity of residence for naturalization purposes. Does that circumstance apply to you? This is a situation that happens to many people who come to the U.S. get the greencard and depart the U.S. for a significant period of time. There are many reasons: ill family member, death in the family, work, finish school, busy selling a home or business in preparation for their permanent move to the U.S.
Ideally, a person immigrates to the U.S. and begins their life in the U.S. and after 5 years can become a citizen. Processing will take a bit of time so, they are allowed to file 3 months early and by the time they show up for an Oath Ceremony, they meet the 5 year minimum.
Even USCIS knows that "life happens". Rather than make a person start over counting a full 5 years all over again after such a disruptive break, they can file after waiting 4 years and 1 day after returning to the U.S. after the long break, if otherwise eligible. If after waiting 4 yrs and 1 day, they still don't have the minimum 4 years and 9 months, then they are not yet OTHERWISE ELIGIBLE. That is why this regulation is refered to as a "remedy". It is not some loophole.
