I've come across this webpage
you cannot be outside of the UK for more than 90 days in any 12-month period in the five years preceding your naturalisation application
This is not aligned with any other source I found, including the Guide AN which states:
To satisfy the residence requirement you should not have been absent for more than 90 days in the last 12 months.
If you are married to or in a civil partnership with a British citizen the total number of days absence for the whole 3-year period should not exceed 270.
Otherwise, you should not have been outside the UK for more than 450 days in the 5-year qualifying period.
Absences totaling more than 90 days seem to be allowed as long as they are not within the last 12 months
One more interesting statement is made in the document:
Nationality policy: Naturalisation as a British citizen by discretion
This guidance tells Home Office staff how to consider applications for naturalisation as a British citizen
Quoted from section: Future intentions requirement
subsection: Principal home in the UK
If applicants say their intention is to have their principal home in the UK, you should accept that they meet the requirement if they:
there is no information to cast doubt on their intention, for example:
a recent absence from the UK for a period of 6 months or more
This is indirectly saying that it would be ok an absence up to almost six months, it obviously wouldn't have to completely fall within the last year