I think that the requirement for the naturalisation application to be made from within the UK is implied.
To begin, it is hard to calculate your absences from the UK when you are currently in the middle of an as yet open-ended absence (because you are absent from the UK at the time of application).
In any case, the
caseworker guidance for naturalisation is clear.
(Page30)
If the applicant is abroad or is about to go abroad for a continuous period of more than 6 months, you should normally refuse the application and advise the applicant to re-apply, on their return to the UK, for permanent residence.
An exception may be made to the general rule, however, where any of the following apply:
• the applicant is undertaking voluntary work such as with the Voluntary Service Overseas (VSO)
• the applicant is undertaking studies, training, or employment abroad which is necessary to pursue a UK based profession, vocation or occupation
• the absence forms part of an established pattern, such as in relation to employment at sea and the applicant is primarily based in the UK
Remember that a naturalisation application is an application at discretion. The only British citizenship applications that I know of that can be made from abroad are ones where the applicant has an entitlement to British citizenship, typically through having been born in the UK or having a British mother born in the UK before 1983.
I am not a lawyer or immigration advisor. My statements/comments do not constitute legal advice. E&OE. Please do not PM me for advice.